MORE MEMORY LESS LABOUR

In the second of our fast storage reviews, we compare the SPDOS and BETA systems.

Last month we looked at tape-based fast storage systems for the Spectrum. This month we turn our attention to discs, one of the first and one of the latest, those from Technology Research and Watford Electronics.

The Spectrum is seen by many people as only a games machine. One of the reasons for that is the limitation of having a cassette interface. The BBC, Commodore and Amstrad can all have disc interfaces designed by the manufacturer; the Spectrum had the microdrive.

That delay caused a number of manufacturers to design disc interfaces for the Spectrum but, as yet, none has been accepted by software houses as a standard. Until that happens users will buy their software on cassette, and then convert it to use on disc.

The Beta system from Technology Research was first reviewed in Sinclair User in March 1984. Since then it has undergone a number of improvements and is now the best selling interface on the market. SPDOS from Watford Electronics has been released recently; it has the backing of a company which has made a name for itself by designing and selling interfaces for the BBC.

Both interfaces will accept both 5.25in and 3in drives in 40 or 80 track, single or double-side format. SPDOS can also accept old 35 track drives. Up to four drives can be used but each must have its own power supply as the Spectrum does not have any spare capacity. Many of the drives advertised as suitable for the BBC do not have a power supply and that can cost another £30.00.

The most popular system is 5.25in and discs cost between £1.75 and £3.00 each. The amount of information they can hold will vary according to the drive and the system used to record it. Both interfaces use a form of double density recording; Beta divides each track into 16 sectors of 256 bytes per sector, whereas SPDOS uses 10 sectors of 512 bytes. A 40 track, single-side drive, allowing one track for the directory, gives 156K and 195K respectively.

The speed of a system depends on several things, including the speed of the drive. All discs spin at 300 rpm, five revolutions per second - but the time it takes to move from track to track will vary. Both systems can work at a number of speeds, from 6ms to 30ms for SPDOS and 6ms to 48ms for Beta. The Beta also incorporates a one second delay, if the drive is not spinning, to allow for older, belt-driven drives to reach operating speed.

Another factor is the method of reading the sectors; Beta follows the usual practice of reading alternate sectors, so the disc has to make two revolutions per track, and SPDOS can read the sectors one after the other and so should be quicker.

The Beta interface, unusually, lies flat from the back of the Spectrum, consequently it is compatible with all full-sized keyboards. It has a through port for other add-ons and is compatible with both the Kempston E printer interface and Sinclair Interface 1. On the right is the connector for the disc drives, which follows the same standard as the BBC and has been successfully used with a BBC drive. To the left is a socket for the Spectrum power supply.

On power up you are presented with the copyright notice and an invitation to enter a password. This is the only system which uses passwords, which can be any combination of characters; if you are forgetful you could give all your discs a password corresponding to the ENTER key and so you need only press that in response to the prompt.

You are then into the DOS - Disc Operating System - and presented with:

A >

to remind you that you are in the DOS and that the default drive, the one to which all commands will relate, is the A, or number 1, drive. You can now use any of the DOS commands directly or enter Y to RETURN to BASIC. You can return to the DOS at any time by entering RAND USR 15360 but that is rarely needed.

All the normal Spectrum tape commands, apart from VERIFY, can be used by the disc: the command is simply preceded by RAND USR 15363: REM:. If PRINT USR or LET variable = USR is used then the number returned will be the error message, 0, meaning no error. Calculated parameters or variables can be used as with the tape command.

There are only two variations: by adding a third parameter when saving CODE it can be made to auto-run, and then RUN, rather than LOAD, must be used to auto-run a program. That applies to both CODE and BASIC. When LOADing and SAVEing if the second character of the file name is a colon and the first is A, B, C or D then the command is taken to apply to that drive. That is a useful way to avoid changing the default setting.

The commands that relate only to the drive are ERASE, which will erase a file, CAT, to obtain a catalogue, USR, which can be used to change the password on the disc and NEW, to change the name of a file. MOVE has a special use. When the system saves information to the disc it is stored, in the interests of speed, in successive sectors; when files are erased gaps are left and MOVE simply moves the files up to fill the space. PEEK and POKE can be used to randomly read information from, and send it to, the disc. To change the default drive *"x:" is used where x is the drive. All those commands must have the usual prefix.

The utility disc supplied with the system contains two other commands: FORMAT, to format the disc, give it its password and an identifying name; and COPY to copy a single file or the whole disc in one go. If you have only one drive then prompts are given to swop the discs.

The instruction booklet gives examples of each of the commands and is written with the novice in mind. Details are also included on how to use the system from within your own machine code programs. The assembly listing included for that contains an error, having the line LD (nn),nn, which must be changed to include a register. The index at the back lists the commands, error messages and pin-outs.

The SPDOS, unlike the Beta interface, sits up vertically from the back of the Spectrum. It has a through port for add-ons but is not compatible with Interface 1. The lead for the disc is connected on the right hand side, using a disc connector onto the PCB, like the TRS80. On the top at the front is a LED and a reset button. The lead for the power supply has to be threaded through a hole in the interface. It will fit most full-sized keyboards, the only exception being the Transform which is rather high at the back.

Powering up, or pressing the reset button, automatically loads the operating system into memory. If a program has been saved with the name "AUTO", in upper case, then that will also be loaded. If the program is in BASIC and was saved using LINE then it will auto-run. CODE will auto-run from its first address.

As with the Beta all the normal tape commands can be used in the usual way, apart from MERGE which will always auto-run. To make them relate to the disc they must be preceded by PRINT #4:.

The commands that relate to the disc, which must also use the PRINT #4 prefix, are: CAT, to obtain a catalogue - this can be followed by a string so that only those files containing the string are listed; CLEAR which performs a block delete; ERASE to erase a file - this includes a wild-card facility where A can stand for any character; MOVE renames files or can be used to copy them.

SPDOS supports sequential files and a number of commands are used for that: OPEN # and CLOSE # are used to open and close files; PRINT # sends information while INPUT # and INKEYS # are used to read it back. To use FORMAT the original system disc has to be in the current drive. That gives the disc its identifying name. Unlike the Beta system errors are returned as a Basic error message.

The system disc contains two other system utilities. The first of those is "copysys", a program which will copy the system, except for FORMAT, to another disc - necessary if you want to use CAT on the other disc. The other program is "minidos", a stripped down version of the system which does not, as far as is apparent, include the sequential access commands. Also on the disc is a simple address book program which shows the use of sequential files plus three commercial programs, Tasword II, Masterfile and Omnicalc 2. Those have been converted to use the system and include demonstration data.

Choosing between the two systems will depend entirely on what you want to use a disc system for. Both are very quick; using the same test program as last month that is,

10 FOR n = 1 TO 30
20 SAVE ("test"+STR$n) CODE 32000,200
30 NEXT n

- and changing line 20 to suit the system, SPDOS took 58 seconds in saving, 23 loading and 29 erasing while the Beta took 55, 33 and 47 respectively. Formating depends on the number of tracks and sides; with an 80 track, single side disc SPDOS took 2 min 43 seconds and Beta 1 min 10 seconds.

If you only want to write your own programs then SPDOS with its overlays, sequential access and faster loaing times has the edge.

If you also want to put your favourite commercial programs on disc then the Beta system is more suitable, unless you are into machine code. The system occupies just 112 bytes of memory below the Basic program area; it also uses the printer buffer when loading code but when doing so it saves the buffer to the disc, carries out the command, and then reloads the buffer.

Both systems allow for a large number of directory entries, Beta 128, and SPDOS 144. With the latter you have more space per disc. Both require additions to the commands, the syntax for SPDOS being slightly easier to enter from the keyboard. Both sell for similar prices, Beta £99.00 inclusive, SPDOS £99.00 plus VAT.

The winner in the contest between the disc drives will be the one which receives most software support. Both companies claim to be talking to software houses. In the meantime more systems are due to be launched. Next month we look at those, including the new system from Thurnell Electronics, priced at only £150.00 for both inteface and drive.

Watford Electronics, Cardiff Road, Watford, Hertfordshire. Tel. 0923-40588

Technology Research Ltd, Unit 18, Central Trading Estate, Staines, Middlesex, TW18 4XE. Tel. 81-63547

MUCH BETA

Technology Research has upgraded its Beta disc interface for the Spectrum, and it is now probably the best stand-alone disc interface for that micro. TR has put all the commands in ROM, added sequential and random access files, provided auto-boot and made it possible to transfer any program to disc.

The new Beta, called Beta Plus, uses a system similar to the Mirage Microdriver. A tape-based program is loaded as normal and then at any point a 'Magic Button' on the interface can be pressed, which transfers the entire 48K to disc. When that is loaded back, the program continues from the point at which it was saved.

The system has some limitations in that it always saves that file under the same name in the same place on the disc, but once saved the file can be renamed and moved around. Unlike the Microdriver, which sometimes has problems fitting two programs on a cartridge, the increased capacity of a disc, 156K with a 40-track drive and up to 636K for an 80-track, double-sided drive, means that you can transfer your entire library to disc.

As well as the 'Magic Button', the Plus now has a reset button. When that is pressed, and on power up, the interface looks for a Basic program, 'boot', on drive one - up to four drives can be used. It also checks to see what sort of drive is connected, 40 or 80-track, single or double-sided, and the stepping rate. When another drive is used that check is made again so you can mix different types of drives.

In addition to the existing commands, LOAD and SAVE of Basic, Code and Data, MERGE, CAT, ERASE, NEW (Rename), MOVE (Compact), and PEEK and POKE (sector read/write), the ROM has been changed so that the Break key can interrupt an operation. The Password is no longer required - old discs can still be read - and FORMAT and COPY are included, plus the new filing commands.

The main additions are the sequential and random access files. A sequential file is opened using the usual OPEN # command, followed by the file name and then either a W, for write or an R for read. Information can by PRINTed to and INPUT from the file.

A random access file is opened in a similar way except that the file name is followed by the keyword RND and a number denoting the record length, up to 254 bytes. Records can be PRINTed to and INPUT from the file at any position.

Technology Research still includes a disc with the interface including a number of utility programs. Those include an enhanced CAT which gives details of file size and start address, FORMAT for old style drives, and a rudimentary tape to disc copier which copies all normally saved files, including Data, to disc.

For a stand-alone interface - one to which you can add your own drives - it is well priced at £109.25 including VAT, plus £2.00 p&p. Existing owners of the Beta can upgrade for £19.95 plus £4.00 p&p.

With the 'Magic Button', Technology Research deserves to have a winner with the Beta Plus; it could be the start of a new era.

Technology Research Ltd, Unit 18, Central Trading Estate, Staines, Middlesex TW18 4XE. Tel. Staines 63547.

STORAGE AND RETRIEVAL OF PROGRAMS

Spectrum owners are being fated with an ever increasing number of alternatives to the humble cassette. The three devices here all offer fast program storage at a reasonable price. The Sinclair Microdrive has been around for over a year now and has undergone various attempts to improve its reliability.

It has now appeared in a pack with the interface and some software called the ZX Expansion System priced at £100. The interface also has an RS-232 port and a network. The operating system is simple to use allowing programs and data to be saved on the Microdrive. Data is stored by opening a channel and then writing data to it. One drawback with the system is that some games cannot run with the interface attached, as the operating system will grab some of the Ram. The software comprises of the popular Tasword 2 word processor, a database, Ant Attack, Games Designer and a spare blank cartridge. The number of Microdrives can be linked up, each further drive costing £50. The cartridges cost £5 each and hold about 80K.

Along very much the same lines as the Microdrive comes the Wafadrive from Rototronics. The unit has two drives, RS-232 and Centronics ports and comes with two wafers and a word processor for £130.

Although noticeably slower than the Microdrive, this unit scores in several areas. It is said to be more reliable than the Microdrive and the operating system is more informative. The directory command gives more than a list of files like the Microdrive. The formatting command also gives a full report of the state of the wafer.

Unlike the Microdrive, it does not grab any workspace until initialised with a simple New* command. Also, should you wish to back-up a file from one drive to the other, you can do so without upsetting the contents of the memory. It saves data in a similar manner to the Microdrive.

In an attempt to make up for the slower speed, the wafers come in three sizes: 16, 64 and 128K. This obviously means that the average access time on the 16K Wafer will be lower. Thus you could load the main program from a 64K wafer in drive one, and have the data you wish to continually read and write on a 16K wafer in drive in two. The wafers are also cheaper at under £4 each.

Moving away from fast tapes to discs, the Beta Disk Interface from Technology Transfer allows you to interface the multitude of disk drives available for the BBC to your Spectrum. One point to bare in mind though, if the drive uses the Beeb's power source, you will need to buy a power supply.

Having got over that hurdle, the system is fast, user friendly, and of course, at £1.50, the discs are much cheaper than wafers or cartridges. The DOS has all the usual commands you'd expect and you can switch it in and out as needed. It even has a disc password system to keep your software from prying eyes.

You also get a free utility disc with the system with the various utilities they didn't have room for in the interface's Rom. The interface can be used with single or double density, single or double sided drives, and up to four can be connected to the one interface.

The system's major limitation at the moment in that data cannot be loaded or saved on disc, but Technology Transfer promise a new Rom in the new year and will upgrade existing units. The interface costs £97.25 for single density and £109.25 for double density.

Which of these systems you go for really depends on your priorities. Although the Sinclair product is the cheapest, the cost of the cartridges makes it less competitive. The cheapest medium of all, are the discs at £1.50 each. If you've got a collection of 40 discs or so, then the disc drive will have paid off.

Disc Interface
Spectrum
£95.00

Technology Research has modified its Beta interface to include a magic button which, rather like Interface III, takes a memory image and dumps it to disc, allowing you to back-up protected tape software to disc. The interface itself was reviewed in January and Technology Research are on 0784 63547.

FLOPPY DISCS AND THE SPECTRUM

Is it possible? Ray Elder investigates.

One late summer morning found me meandering towards Staines. In an issue of ZX Computing I said Technology Research Ltd. had not seen fit to send one of their disc drive interfaces for review. However since I wrote that, and before the issue reached the newstands, they had offered me one.

Needless to say they were quite indignant at what appeared to be a complete falsehood, but during the ensuing phone call they accepted my explanation and invited me to visit their premises. Well, a chance of a day out was not to be missed, and so off I went.

The Staines central trading estate was well signposted and easy to find. It is a large, sprawling complex of offices and warehouses and a great deal of activity was taking place.

I was directed to TRL's office where I was met by Mr. Rutherford the general manager, a pleasant gentleman with a wealth of experience in marketing and who is certainly nobody's fool. He introduced me to Steve Tam who is the marketing director and to Steve Mok, managing and technical director and who is the inventor behind their products.

The workshop is just what you would imagine such a place to be, racks of components, strange looking half finished gadgets and a steady hum of activity. Everything is done to a high degree of accuracy, an automatic flow soldering machine has been purchased to ensure the most reliable soldering and to remove the chance of dry joints.

I had asked for a loan of an interface, but here Mr. Rutherford showed his business acumen and gave us one, as he said; "If you have it on loan you'll mention us once in your review, if you have it permanently then you'll be able to try it out with the latest devices as they are produced and keep mentioning it with regard to compatibility." Regular readers will recognise this as being true as I'm always mentioning the ZX Lprint III interface and DK'Tronics keyboard!

MERGE

Back at the office I blythely mentioned that I had a disk interface and asked if there was a spare drive I could use. "What type? What connector? What DFS or DOS?" the experts asked.

"No idea" I said, "don't you just plug it in?"

The gales of derisive laughter at my ignorance somewhat dampened my confidence. As it turned out there wasn't one there anyway. So I contacted some of the companies who sold disk drives, the reaction was much about the same but also there was a feeling of disbelief. A disk drive for a SPECTRUM???

Eventually I phoned Viglen, their attitude was similar at first but soon changed to one of interest and they agreed to provide me with a drive. By now I was able to inform them that it was a standard Shugart connector - I'd read the interface manual!

VERIFY

Sure enough, two days later, a huge parcel arrived inside of which, and taking up approximately 1/20 the space but very well protected, was the disk drive.

Plug the interface into the back of the Spectrum, a tight fit normally, but with the DK'tronics keyboard very much so. In the end I used the Currah micro slot extender/port divider between the interface and the Spectrum, a much better fit all round. The interface has a full port at the rear and I tried the ZX Lprint III Centronics interface there first. It worked but the overall depth of the system was now nearly 3 times that of the Spectrum! I found that is still worked fine in the top of the Currah slot so I left it there and connected the PRISM VTX 5000 Prestel/Micronet telephone system to the back. Plug in the disk drive connector cable to the socket on the right side of the interface, plug in the Spectrum power supply to the special socket on the left of the interface, held my breath whilst keeping my fingers crossed and switch on...

LIST THE TRL INTERFACE

The B Disk interface, as it's called is a large black ABS box which lies flat and plugs into the rear port of the Spectrum, a full through port is provided as well as sockets for the Spectrum PSU and the drive cable.

It is a nice looking unit and as was to be expected, the component layout and soldering was tidy and neat.

The accompanying manual is a joy to read, I read it first while waiting for the drive to arrive and could understand it without having to have the thing working in front of me to experiment on.

In a clear and concise manner each of the functions are explained, all the standard SAVE and LOAD formats are provided plus a facility to auto run machine code by specifying its run address as a third parameter when saving. Verify is not supported and this worried me at first. However, after extensive use, I can honestly say that I've never had a failed SAVE.

Some Microdrive commands are used, ERASE, CAT and MOVE to tidy up the disk, and up to four drives can be controlled from the interface.

On power up the interface is automatically brought in, the TRL notice is displayed and the disk password is requested. Each disk used can be protected by its own password. Once this is entered then the interface cursor is displayed, you can then utilise the disk commands or, by entering RETURN, go into Basic.

The Microdrive file system is operated by the Streams and the functions OPEN and CLOSE are not used. Steve said he's working on it, but I can see no immediate necessity as, to my knowledge, there is no commercial software using it and there are many ways of getting around it.

A useful device is the use of PEEK and POKE in disk commands which will allow you to have random access to any sector of the disc, a competent programmer could make use of this to access the 255 bytes for filing.

The disk commands can be accessed from within both Basic programs and machine code programs. Brief but full instructions are given in the manual.

VIGLEN DISC DRIVE

Viglen are essentially a computer supplier and were interested in the idea of linking a disk drive to a Spectrum, I got the impression from some companies that they couldn't be bothered with such a lowly computer.

Viglen have a large range of drives available at a large range of prices, but the one I asked for was a very simple, 40 track, single sided drive plus built in PSU.

The one supplied was the TEAC FB501 and bore their legend. The cost for this unit is £159.00.

The drive itself has a smart, long thin cream case with a black front, disks are inserted and a lever secures them, apart from a slight rumble as the drive starts and stops, operation is almost silent.

The case dimensions are, 146 x 41 x 209mm, and it weighs 1.4 Kg. Ie. It's bigger and heavier than the standard Spectrum! There's not much to say about the disk drive except that is has performed perfectly and to recommend the company to you as they were very helpful.

RUN

CRASH!! Oh dear; however the problem was soon traced down to the incompatibility of the VTX 5000 and the interface. Both wanted to initialise and operate on power up.

TRL were again helpful and suggested a simple modification which would overcome this. In effect, to cut out the auto start up all that is needed is a small, single-pole, two-way switch. They offered to modify my interface and said that for a small charge they will fit it to anyone's interface if required. It seems a pity that it couldn't have been built in as standard.

After that all worked perfectly.

The interface uses an incredible 128 bytes of the Spectrum RAM, and, apart from the usual problems which all microdrive owners trying to convert programs encountered, getting programs onto disk was simplicity itself.

Programs which were written in a professional manner for serious purposes were obviously provided with suitable documentation which made it easy.

Tasword II , probably the most widely used and professional word processor was converted in twenty mins (including 4 mins loading in from tape: disk load time 8 sees.)

Masterfile from Campbell systems, the most versatile filing program I have so far seen for the Spectrum also transferred as if it was designed for disk.

So I tried Jet Set Willy. No problem!

Here is a comparison:

Jet Set Willy loading times

Tape - 4.30 mins.

Microdrive - 9.50 to 4 5.15 secs, depending one tape position.

Disk - 11.10

REM

TRL demonstrated the interface working with the Sinclair Interface 1. It is fully compatible with it, so that the RS232 and networking facilities can be used.

This is particularly useful in an educational situation as it means that several Spectrums can have use of a single disk drive through a central controlling Spectrum.

The latest device from TRL. is a Centronics interface for the QL which plugs directly into the RS232 socket. This should cost around £45.00 inc. VAT and on the production model I saw the unit was built into a connecting cable.

A similar unit is planned for the Spectrum Interface 1 RS232 port and should be available soon.

OUTPUT

Very impressive indeed, but also expensive at £85.00 for the interface plus £159.00 for the drive (£244.00) this is not likely to be the system for the occasional user.

Indeed, if your main use is games and all you want is to get at those aliens quicker then the Microdrive is more than adequate. A disk system would be a waste of money in this case.

However, if you take your hobby seriously or use your Spectrum for any business purpose, then this system is well worth considering. In the long run the price of disks compared to that of microdrives - £1.90 to £4.95 - is worth noting.

Disks, although not the perfect storage medium by any means, have been around for a while and the drives are well tested and usually reliable.

And finally, if you get something like a disk drive it is almost certainly going to be compatible with another computer if and when you upgrade from your Spectrum, whereas the Microdrive almost certainly will not.

THE SPECTRUM BETA PLUS DISK DRIVE

A look at a new version of an old favourite.

Technology Research Ltd. presented us with their new Beta Plus with an air of pride. Outwardly it looked the same as their old interface, a large box which lies flat behind the Spectrum, but with the addition of two small buttons. However the capabilities are greatly improved. To briefly recap on the original specifications for readers who missed our review is probably a good idea.

The interface connects to the port at the rear of the Spectrum and has a through port on the back to connect further peripherals, it is fully compatible with the ZX interfaces 1 and 2, and has a power supply socket - using the original Spectrum PSU - on the left and the disk connector on the right.

Up to four drives can be connected and these may be any type, 40/80 track, single or double sided, and in any combination. They must however be double density drives and have their own PSUs.

A new feature of the interface is that the system checks the number and type of drives connected and operates them automatically when performing such operations as Format. Very clever. All the standard SAVE/LOAD operations are provided although VERIFY is not. After continual usage over a twelve month period with the first version, I have never had a failed save.

The original version did not provide sequential loading and saving a 255 byte sector of code was included. The new version is greatly improved by the addition of both sequential and random access file compatibility, the latter of which speeds up file operations. This was one of my few criticisms of the original.

The interface takes a mere 128 bytes of memory for its own use and is easy to use even if you only have a minimum of programming knowledge. The manual is a perfect example of how to write in a simple, clear manner yet contains all the information any user could require. Converting such programs as Tasword II or Master file, two of the most likely programs to be used with a disk system is very simple and takes only around ten minutes, and four of those are loading the original from tape!

The interface has proved to be compatible with all the disks used with its predecessor.

EXTRAS

Especially interesting to those such as myself who enjoy playing games as well as using it for business is the new 'Magic Button'. This performs the same operation as the Miracle Microdriver does for Microdrives, in that the whole of the Spectrum's RAM memory is dumped to disk by pressing the small button at the rear of the interface.

This means that ANY program can be copied to disk, at least, I tried it with some twenty games which included those with different fast loaders and protective code, and all saved without problem.

There is a very slight problem in that this operation uses the first tracks on a disk, overwriting anything already there. This means that having used this operation you have to rename the file (all files so created are initially given a space as a filename) and then, using the utility provided on disk, transfer it to another disk. In this way I found you can store three programs on a 40 track single sided disk plus a main 'auto boot' menu program.

Oh yes, on power up or on pressing the little reset button on the side of the interface you now have the ability to automatically load and run a program called BOOT on the disk. If there is not such a program present then the system gives a disk error report and you can continue as you wish.

One thing that worried me at first was that, because of the automatic sensing of the drives, the drive is activated and the light remains on if no disk is in it on power up. Apart from giving me a moment of concern and frantic call to TRL who assured me this was correct, this has no effect and, on inserting a disk, the drive whirrs and settles down. No ill effects to the disks have been experienced.

The updated utilities disk provides more powerful programs to backup, catalogue and copy files and each is simple to use, and a valuable bonus. Owners of the original TRL disk interface need not feel left out as they can update it for £23.95 inc. VAT & P&P, a reasonable price and well worth having done.

The interface is on sale direct from TRL at £111.25 inc. VAT and P&P.

OPINION

This is now THE disk drive interface for the Spectrum, I know of no other which provides such a comprehensive range of operations and facilities.

It's nearest competitor is the excellent Discovery all in one unit from Opus which, although lacking some of the TRL features has a few different ones to offer, such as printer, joystick and video ports. However TRL gave me the distinct impression that they have not finished with theirs yet...

Technology Research Ltd., Unit 18, Central Trading Estate, Staines.

YOUR FLEXIBLE FRIEND

Two disk arrangements, based on completely different ideas, have been available for use on the ZX Spectrum for some time now. Stephen Adams compares and contrasts the Viscount interface and drive from Spectrum Computer Stores and the FDI interface from Technology Research Ltd.

The object of buying a disk drive is to be able to speed up LOADing and SAVEing of data and programs - data being the most important, as files used for databases frequently have to be LOADed, MERGEd or altered and then SAVEd again.

One advantage these disks have over tapes (including the ZX Microdrive) is that it's possible to go directly to an area (or record as it's called) of data and read it directly into the computer. This is called Random Access. Of course, on tape, the whole thing has to be gone through right up to the point where a particular record is found. And if it's not found then the tape has to be re-wound and the search begun all over again. This laborious process is known as Serial Access.

Another advantage is speed. The baud rate for LOADing data from disks is usually in the region of 128K baud as against the Spectrum's tape speed of 1500 baud, an increase of about ninety times! Double density disks and multiple drives can also raise the amount of data immediately available to the computer. The approximate data capacity of the systems examined here is about 100K minimum.

In both cases, connection to the ZX Spectrum takes place via the expansion port, but only the FDI provides you with a further expansion port at the back for attaching printers and the like. To use a printer with the Viscount, you'll need a special flexible cable with extra sockets that contain printed circuit cards. These are available from CPS (wholesale distributors for all Sinclair Research 'out of guarantee' spares) as well as Spectrum dealers.

Both systems use up memory space for the Disk Operating Systems (DOS) at the top of memory. The Viscount, because it's software controlled, uses up more memory (8K) than the FDI which normally only uses 1K. However, the FDI swallows up an extra 4K as a buffer for deleting files, and this needs to be allowed for when writing or modifying existing programs. And remember too that many machine code programs such as Tasword are position dependent in memory and you'll need a new version to work with disks.

Having inserted the interface in the back of the ZX Spectrum, powered up the disk drive (the FDI interface takes BBC disk drives, so the choice is a wide one) and switched on, what do we get now? Well, on the Viscount we notice no difference at all except that there are now two copyright messages on the screen, and RAMTOP is 8K lower. With the FDI you are straight into the DOS and the system requests a password. This is 'TRL' (supposedly standing for 'Technology Research Ltd') for the disk supplied, but you can change it to anything you like. Only the correct password (which is recorded on the disk when it's formatted) will allow you access to the directory (a menu of the programs on the disk) and thus to the files.

Once through the password you may enter a command for either A or B disks (if you have a dual drive system) from the table listed at the end of this article. This command will then be executed by LOADing and RUNning the file named. You can return to Basic, but this NEWs any resident program.

Life is a little easier on the Viscount. You can LOAD a program from tape, enter a program or LOAD one from disk using the variables already inserted into the variables section by the DOS. All commands must be put into f$ in the form of name and the details of the file you wish to LOAD or SAVE. By file (as you might have already guessed) we mean a program, data array or machine code routine. The commands on the Viscount are easy to use, consisting of a call to a machine code routine in the DOS using instead of numbers, a variable which is a reasonable description of the command. For instance, 'RAND USR BL' LOADs a Basic program, 'RAND USR BACK' makes a back-up copy of the disk, and so on. These must be re-loaded if you use RUN or CLEAR by RAND USR 64000. The names can also be changed to suit the program - for instance, you might change BL to 'DATABASEPROG' and CL to 'FILELOAD'.

The only problem I found using these commands is that there's an error in the BACK routine which requires POKEing locations 63208 with 80 and 63209 with 249. These I eventually SAVEd as a code program which could be loaded up before using the command. The DOS may therefore be modified in both systems to eliminate errors.

I also had some trouble with the disk units themselves. They tended to overheat when I first got them, but this I cured by installing larger heatsinks on the power supply; there's been no trouble since. Problems on the TRL system centred mainly around the fact that I couldn't format my double-sided disks, despite trying several different sets of software from the suppliers. Eventually, I switched to a single-sided, single drive system which worked fine.

A word of warning, however. The interface socket, although quoted as BBC compatible is in fact upside down to the normal connector. Therefore, the notch on the plug does not go into the hole provided on the socket - at least not without causing damage to the interface. There's a listing of the pin connections in the manual, but no warning.

VIVE LA DIFFERENCE!

The FDI is designed to cope with machine code programs, mostly with the user allocating a buffer for the routines or data. Basic programs (using an 4$' prefix) can be LOADed or MERGEd, but the variables (with a '#'' prefix) must be SAVEd and LOADed separately. Any program without a prefix is a machine code program which is LOADed and run from the location given. Basic programs may only be RUN on LOADing (no GOTOs). The commands PUT and GET allow you to SAVE and LOAD data in 512 byte machine code sectors into a buffer.

The commands in Basic must be POKEd into a workspace contained in the 1K area; but a USR routine must first be called to find out where. After POKEing the command in, a list of numbers within the command must also be POKEd into another series of locations. Then, the USR routine which looks at the line can be called.

Although a Basic subroutine was included on the disk, which could be MERGEd with the main program (so that strings could be used to give the commands), I still found it cumbersome and would hardly call it user friendly!

The FDI moves all programs and so on around to take up any spare space - which is very efficient. This means any new file is always added on the end of the list. The Viscount, however, only allows you to use complete tracks for files, which are 2816 bytes long. Thus if a program or data is only 20 bytes long it still takes up 2.816K.

Arrays can be stacked together in one file to give better use of the space and member numbers act like DIM numbers for the particular array you want.

TOP OF THE FLOPS?

Both manuals are reasonable, given that they've been written with the programmer in mind and not the average user. The Viscount is perhaps slightly better in that it lists the error numbers at the back - the FDI manual leaves you to find out for yourself! Taking everything into account, the Viscount would seem to be the better system. It not only costs less, but is far easier to use; it also includes a back-up program (very important when using disks), whereas it's an optional extra with the FDI.

DATA

The Viscount is only available at present through the Spectrum chain of dealers, but may also be stocked by other sources as it becomes more popular. The disk drive plus interface costs £245.

Technology Research Ltd is at 356 Westmount Road, London SE9 1NW (Staines 63547). The FDI interface costs £99 and needs a BBC or similar disk drive (self-powered); TRL's equivalent to the Viscount disk costs £218.50 and a connecting cable adds perhaps a further £15. The copying program (to back up the disks) costs an extra £7.

Both systems reviewed here require the 48K Spectrum. However, the FDI interface can also be supplied for the 16K machine.

HARDWARE WORLD

With ever-increasing amounts of peripherals available for Sinclair computers, users are finding it more and more difficult to know what to buy. We present a buyer's guide to joysticks, keyboard and printers and review the best of the rest from the 1984 add-on market.

The last year has brought about a vast change in the sort of add-ons available for the Sinclair machines. Many are technically brilliant while some would have made Heath Robinson blush. There are few add-ons still being produced for the ZX81, with even fewer new ones, but there has been an avalanche of Spectrum designs, and the start of what promises to be an interesting range for the QL.

The most popular areas of interest - printers, joysticks and keyboards - are dealt with in separate sections but there have been some very innovative designs produced in other areas.

BETA DISK INTERFACE

With Interface One now widely available and users turning their attention to fast storage, floppy disc systems are now available for the Spectrum. The Beta Disk interface from Technology Research has been improved continually throughout the year and now, in its final form, is the best available. It can handle up to four drives of either 40 or 80 track, single or double density format, in any mixture. The connector to the drive has the same format as that of the BBC drives and those can be used with it.

With the interface fitted it is useful to think of the Spectrum as having two distinct states. Either it is using Basic, from whence the disc commands can be called, or it is using the Disc Operating System (DOS); the only difference between the two is the call needed to bring the system into operation. As it uses the standard Sinclair syntax for LOADing and SAVEing Basic, code and data all you have to do is call the DOS prior to the command, which can be done from either Basic or machine code.

On power up the Spectrum runs under the DOS and requests you to input a password; that must be the same as that on the disc you are using. Once that has been done you then have access to the disc commands. As well as the LOAD and SAVE mentioned, which in addition to the normal commands allow you to auto-run CODE, you can CAT any of the drives, MERGE Basic programs, ERASE a file or MOVE which moves up all the files to fill any spaces left on the disc by ERASE. Random access to the disc is by PEEK and POKE.

With all that it only uses 128 bytes of memory which it reserves by moving up the BASIC program area. Normally it is completely transparent to the user and there are very few programs, commercial or otherwise that cannot be used with it, unlike the microdrive.

With a 40 track, single sided disc drive the interface gives 97.5K of file space, the other 2.5K being taken up by the directory. The 80 track version give you 390K. The interface is expensive, but it does allow the use of drives that are not dedicated to one machine and you can use easily obtainable discs which cost less that £2.00 each.

Beta Disk Interface, £85.00, exclusive of VAT and postage. from Technology Research Ltd, Unit 18, Central Trading Estate, Staines, Middlesex TW18 4XE.

THE EXPRESS GANG PART II

The crazy Express gang continues with two slightly more powerful adversaries. In the last issue, Sinclair's MICRODRIVE and the TRITON QD disk drive both provided low-cost fast storage media at for less than £120.00. This issue sees another low cost contender, which is a direct competitor to Sinclair's MICRODRIVE, Rotronic's WAFADRIVE. The WAFADRIVE provides two disk drives, RS232 serial and Centronics parallel output ports for printers and communication handled with the extended Basic commands using streams and channels. In fact, the WAFADRIVE seems to convert the Spectrum into a full specification computer,... well nearly.

The other contender is Technology Research's BETA disk drive with the new updated disk operating system TR-Dos V4, This unit must be a little gem for games fanatics, as it allows them to store their hard-earned cassette software collection to disk for instant recall. If that isn't enough, the system caters for random access data files, where any specified record may be read or written to - no more long wait cycles while skipping to the required record. Although the BETA disk commands reside in the operating system, they may be accessed from Sinclair Basic or machine code. The BETA interface unit is not expensive, but it does exclude the drives, so the complete system reaches normal disk drive price levels, which are certainly above those of the previously mentioned fast storage units.

In the next issue there are more drives to follow, including the KEMPSTON disk interface, the OPUS DISCOVERY and the TIMEX disk systems. The last of this series will feature a comparison table listing all the drives reviewed, so that the important decision of selecting the right drive for the right job will be that much easier...

HARDWARE:

The package consists of the disk interface unit which connects to the expansion port of the Spectrum and a software disk. No disk drives are supplied. The Unit was tested using a twin disk drive unit with integral power supply kindly lent CRASH by Cumana, 'the best memory people in the business' (no chance of them forgetting their equipment on loan!).

The BETA disk interface features a standard Shugart compatible disk drive port at the right-hand side, to which the required disk drive or drives may be connected via a flat ribbon cable. Up to four disk drives can be connected to the system and these can be 40 or 80 track, single or double sided. To the rear of the interface is an expansion port for further Spectrum add-ons and the 'Magic Button' which activates the RAM Image Saver. To the left is situated a reset button.

SYSTEM DESCRIPTION:

On power-up the system boots up in to the Disk Operating System (DOS) environment and not in Sinclair Basic. The interface automatically checks the drive specification and adjust its speed and format accordingly. Access to the disk system is gained by use of the DOS commands. At any time Basic may be called up via a RETURN command. Re entering DOS is via RANDOMIZE USR 15360. The DOS commands can be used in Basic in the form of a RANDOMIZE USR:REM: call, similarly in machine code via a CALL 15363 command after having changed the Basic variable CH ADD to point to an address line buffer. A program stored under the name of 'boot' may be run by simply typing RUN and ENTER. The DOS caters for random access files, which allows proper database operation.

At the press of the 'Magic Button' the running program is interrupted and the whole image of the RAM is be saved on disk. The image may be retrieved from the disk to the RAM with the program continuing to run from where it was interrupted. This means that games may be loaded via cassette in the usual way and once the loading sequence is completed the program may be saved to disk without the change of a single byte in RAM to upset the continuation of the game. This provides a disk copy of any game which runs on the Spectrum and should prove to be a nightmare for any software house if it isn't for the fact that very few Spectrum owners can actually afford a disk system. The disk system requires a buffer of 256 bytes (one sector) and uses the printer buffer of the Spectrum. Before the buffer is used, it is stored on the system track of the disk. When the operation is completed, the original printer buffer data is reloaded from disk. RAM data is only lost if the disk is write protected. The software disk provided with the interface contains a range of useful disk utilities.

OPERATING SYSTEM:

BETA TR-Dos V4

SYSTEM COMMANDS:

CAT lists the files on disk. The listing can be dumped to a channel when the command is extended to CAT# number.

COPY copies specified source file on source drive to destination file on destination drive. Will not work with single disk system.

CLOSE # channel-number closes specified channel.

ERASE removes a file from disk.

FORMAT checks the drive specification and formats the disk. A double-sided disk drive can be forced to format as a single-sided with a disk name starting with '$'. This is essential for use with the RAM saver.

GO TO "filename"CODE loads and runs a saved RAM image.

LOAD loads program from disk to memory. A Basic program stored with a line number will autorun from that line number, otherwise the program will be automatically listed. When loading a machine program, it can be relocated with LOAD "filename"CODE new address.

MERGE merges Basic program with the program in RAM.

MOVE repacks the files on disk.

NEW changes the name of an existing file on disk.

OPEN# channel-number,"filename"W opens a channel for write. To save a string to disk in filename requires a Basic function PRINT$channel-number.

OPEN # channel-number,"filename"R opens a channel for read. To read data from filename on disk requires an INPUT# channel-number; variable.

INPUT# channel-number; (record-number), variable-name reads a record from the file when random access file is open.

OPEN# channel-number,"filename"RND, record-length opens a file for random access.

PEEK reads any required part of a file on disk and transfers the data into RAM. A complete sector is read and transferred to the specified location within the Buffer RAM.

POKE writes a specified sector of data from RAM to any location on disk.

PRINT channel-number; record-number, variable-name writes a record to a file when random access file is open.

RANDOMIZE USR 15360 calls up DOS from Spectrum Basic.

RUN "filename" loads and runs Basic program filename.

RUN "filename"CODE loads and runs machine code program filename.

SAVE "filename" saves a Basic program.

SAVE "filename" LINE number saves a Basic program run from line number.

SAVE "filename"CODE n, m saves a machine code program.

SAVE "filename"DATA a() or a$() saves a variable or character array.

40 informs the system that the currently selected drive is a 40 track drive. Required for drives without an end stop switch.

ERROR REPORTS:

Disk error indication with retry, abort or ignore option. If DOS commands are from Basic or machine code programs, the error code is stored in the Z80 register pair BC. To obtain the error code, a variable is set equal to the DOS command, The variable takes on the value of the error code on completion of the DOS command.

EXTRA FACILITIES:

RAM image copier for storing protected commercial programs on disk. Utility disk contains programs tapecopy and filer, which are disk utilities.

MANUAL:

32 page manual with TR-DOS V4 addendum does not make for easy reading. Includes advice on using DOS commands in Basic and machine code programs, error message coding, pin connections and explanation of disk utilities.

APPLICATION PROGRAMS:

None.

CRITICISM:

- Not so easy access to DOS commands from Basic.
- Confusing doubling up of DOS commands and disk utilities.
- Manual confusing with TR-DOS V4 update.

COMMENTS:

Excellent value disk interface with random access facility and superb Ram image saver for games collection on tape (naughty but nice...)

MEDIA:

Depends on drives connected.

TECHNICAL SPECIFICATIONS:

Number of drives supported per system: 4
Storage capacity: up to 640K (80 track double-sided)
Sector size: 256 bytes
Number of sectors: 16 sectors per track

TIMING:

Formatting: approx 35sec
Cataloguing: approx 2sec
Loading a screen: approx 3.5sec

PRICE:
£109.25 inc VAT Plus £4.00 p&p