WAFADRIVE V MICRODRIVE

The Rototronics Wafadrive is likely to be the main competition to the Sinclair Interface One and microdrives.

The unit is more compact and better designed than Sinclair's, containing both RS232 and Centronics printer interfaces as standard.

The power for the drives is taken from the Spectrum user port and fed through a ribbon connector which is fitted onto the base of the Wafadrive. That connection could be a disadvantage as it limits the range of other peripherals that can be put onto the user port at the rear of the drive.

The large manual supplied with the drive shows that the storage medium contained within the cartridges can have 16K, 64K or 123K formatted capacity, approximately 40K more than a ZX Microdrive.

Before use a tape cartridge has to be FORMATted. Once that has been done the drive will display drive name, wafer name, list of files, type of code, size of each file and how much space is left on the wafer.

Once SAVEd, programs are easily LOADed. The drive is slower than a microdrive but faster than cassette. It is also more reliable than the Sinclair storage unit and all Basic programs run after LOADing from it ran first time.

Backing up programs is easy with the Rotronics unit. Code can be copied from drive A to drive B using the system software supplied by the manufacturer. Cartridges are, however, guaranteed for a lifetime of 5000 hours and, a cost of £3.99 each, they represent better value than the Sinclair cartridges.

One small criticism of the drives concerns the printer interfaces which use push-on connectors. It is possible that they might wear quickly if maltreated and that normal plugs might have been better. The Wafadrive is sold with two manuals, two free wafers, a word processor package together with an extra manual describing its use.

It costs £129.00 and can be obtained from Rotronics Ltd, Santosh House, Marlborough Trading Estate, West Wycombe Road, High Wycombe, Bucks, HP11 2LB.

RACING TO THE TAPE

Speed, economy or reliability? We take three of the fastest systems out on the track for a test drive.

It is now just over a year since the introduction of the microdrive, and in that time it has done more to inhibit the serious use of the Spectrum than any other add-on. Before you put pen to paper and write to us, an explanation is perhaps in order.

Users of the BBC, Commodore and other home computers expect to be able to add a fast storage medium - disc, hobbit and so on - to their computer and to be able to buy software in that format. There is an accepted format for both interfaces and recording medium and therefore software houses can develop programs knowing that they will be able to sell them.

The announcement of the microdrive, roughly a year before it actually saw the light of day, inhibited manufacturers from developing a standard, as Kempston had done with its joystick interface. The stories of unreliability, unfounded or not, also inhibited software houses as they could not ensure that any programs sold on cartridge would always work.

Finally, the price, scarcity and difficulty of duplicating microdrive cartridges gave few writers the confidence to market programs on cartridge. At the time of writing the number of programs available on cartridge can be counted on one hand, with a few more that are 'microdrive compatible', and none which were specially written for it other than copiers.

Despite that the microdrive is undoubtedly a remarkable device. It makes available a form of fast storage which many people would otherwise be unable to afford and, within limits, provides a usable system. It is only recently that it has been readily available and so perhaps now it will be accepted.

Because of those problems and delays, other manufacturers felt that they could do better and so there are now many other fast storage devices available, with more due to be released. While some are undoubtedly better, and more expensive, than the microdrive they all share one common problem, and that is that because there are so many different systems it is largely left to the user to convert software to run on them. With the ever present spectre of software piracy few software houses make their programs open to inspection and, due to the fact that most of the systems take up valuable memory space, some programs can not be converted even if you are able to break into them.

Your own programs, however, should be easily convertible; you are unlikely to write Basic programs in excess of 35-40K, and if you are able to write in machine code then you should be able to move it to an unused part of memory. The problem with commercial tapes is that the usual format is to have a Basic loader program which lowers RAMTOP and then loads a screen display followed by some machine code. It is the lowering of RAMTOP which causes the problems.

A BASIC program unusually starts at address 23755 - chapter 24 of the Spectrum manual suggests that you enter CLEAR 23800 (i.e. lower RAMTOP to that address) to see what happens when the computer runs out of memory. In order to be able to enter a short line of Basic you will need about 100-200 bytes of memory, so the minimum address to which you can usefully CLEAR is 24000, giving approximately 100 spare bytes. With the more popular commercial games it is quite common to CLEAR to 24000-25000 and so you can see that there is not much space left. With a program written for the 16K machine it is not uncommon to clear down to 23900. The simple answer is that the less memory the system takes the more programs you will be able to convert.

A good indication of that is the sector size. With microdrive and disc the data is held in blocks known as sectors. Those blocks are loaded into memory by the system one at a time and then moved to where they are required. For example, with microdrive the sectors are 512 bytes long, so you will need the operating system of about 100 bytes plus 512 for the sector and 83 to hold the additional channel information - say, 700 bytes spare or a minimum clear of 24700, more if you want to use two drives.

Another problem may be that of speed. Almost anything is quicker than cassette; a commercial 48K game takes about five minutes to load, but the method of storage will affect the speed. A microdrive uses a continuous loop of tape and so if the sector you want is next on the tape it will be very quick. If it has just passed that sector then the microdrive will have to go all the way round the tape, and so take longer.

A disc, however, normally stores the data in a number of concentric circles, known as tracks, and each track is divided into sectors. As the disc is spun very quickly those sectors are readily available. Overall, the time it takes to find a sector is largely determined by the time it takes to move from track to track. This can be as little as 3ms, 3/1000 ths of a second.

There is, finally, the problem of reliability. If you are writing your own programs or using the Spectrum for business then the system must be 100 percent reliable. That can only be judged with time and any comment on a new system can therefore only be an educated guess.

The first system looked at was the Challenge Sprint. That is a fairly new system and also the most straightforward. It is, simply, a normal cassette mechanism which has been converted to run the tape at four times the normal speed of 15/16 ips, (inches per second).

A flexible lead plugs into the back of the Spectrum and, on the back of the cassette, there is an extension port. It takes its power from the Spectrum. The Sprint recognises all the normal tape commands, whether used from Basic or code, and therefore is very simple to operate. To load a tape you use the usual LOAD "" command and press play.

The advantage of the system is that you do not have to convert any of your programs. The only programs which it would unable to load would be those which use their own, non-standard, loading routine such as Halls of the Things, or those where the time between the sections of program is very important.

The reduction in loading time is good; Scrabble, by Psion, which normally takes four minutes and 48 seconds to load, now takes only 1.16 minutes. Saving a straight 64K block took 1.15 minutes.

To have a means of measuring the speed of the different systems the following program has been used:

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

with line 20 changed as required. When saving with the Sprint it takes 2.36 minutes, and on loading 2.37 minutes.

The disadvantages of the system are largely the same as those at a normal cassette. You cannot control the cassette motor from software and so you cannot load selected programs without correctly positioning the tape by hand, or running through the whole tape. A note must be kept of the tape counter in order to find a program and, due to the speed, that must be very precise.

The cassette does not have any volume or tone controls and so when loading your own programs it is a case of all or nothing - if a program does not load then it is not going to. You cannot then try to load it using a normal cassette recorder without disconnecting the Sprint as it expects all tape commands to relate to itself. All the commercial tapes which were tested, however, loaded without problems.

The only other possible problem is the speed itself. Cassettes are not designed to be played at the speed at which the unit operates and so, despite having a good system which accelerates the tape to playing speed, when using Stop, Fast Forward or Rewind sudden speed changes occur and the tape is liable to stretching. The only way round that would be to only use those commands when you are certain that there is nothing on the tape at that point. It will Autostop from Play at the end of a tape.

Surprisingly, some people want to use the Sprint with their microdrives. Early versions were not compatible with but that is now being corrected. When ordering it would be best to state if you intend to use it with a drive or not.

If all you want to do is load commercial tapes faster than normal and you do not want to worry about converting then this is the system for you. It is easy to use and provided the above points are remembered it should prove reliable.

The Sinclair microdrive has a number of good and bad points but it is the least expensive way of adding a fast storage/random access device to the Spectrum. Sinclair is selling currently a package of Interface 1, microdrive and four software packages for £99.95. The software is Tasword II and Masterfile, both of which are easily convertible anyway, and Ant Attack and Games Designer from Quicksilva. An introductory program and spare cartridge are also included.

The amount of space taken up by the operating system, and the increased length of the commands, have caused some users to experience difficulties in converting tape-based programs to run on it. Some games, such as Jet Set Willy, are easily convertible while others, such as Sabre Wulf or Scrabble present difficulties. In some cases it should be possible to modify the Basic loader program, either by standard memory saving techniques - such as using VAL or PI/PI to cut down the number of bytes used by numbers - or by loading the Basic in more than one part. If you are able to write your own machine code routines then a system of using the screen as a buffer, moving the Stack Pointer and then a block move will work in most cases.

Each of the cartridges can hold a minimum of 85K of data. That can sometimes be increased by repeatedly formatting it, each Format command taking 24 seconds.

Using the test program given above the microdrive takes 3.42 minutes to save and only 14 seconds to load. If, however, line 10 is changed to:

10 FOR n = 30 TO 1 STEP - 1

so that the sectors are not loaded in sequence, it takes 3.15 minutes. Erasing also takes quite a long time as a number of checks are made by the system when that is done. Using the test program with line 20 set to Erase it takes 3.46 minutes. Simpler commands are much quicker, a 64K block is saved in 18 seconds and CAT performs in only 7.5 seconds.

As well as the usual tape based commands for BASIC, CODE and DATA it is also possible to open files to the drive and send information to it. That can be very useful but it presents two problems. Every channel which is opened takes up memory and the data can only be accessed serially, so if you want the last piece of information on the file you have to Read all the way through it. That can be time consuming.

To run a microdrive you also need Interface 1. That gives you a RS232 port, useful for running a modem or printer and a network facility. Both are very useful additions but unfortunately most low-cost printers use Centronics rather than RS232 and the add-on kit for an Epson printer, for example, is in the region of £70. Moreover, while Spectrums can be networked there is some confusion as to whether or not the system will work with a QL, and if not that will mean additional software, on top of the 276 bytes used by the system.

Whether you love or hate the microdrive it cannot be ignored. If your pocket will not stretch any further then it is worth consideration, but bear in mind that it cannot be used on any other computer and so when you upgrade your system it will no longer be of any use. The manual supplied with it is not up to the usual high Sinclair standard, so you would do well to get one of the many books published about it. Mastering Your ZX Microdrive, by Andrew Pennel, Sunshine Books, or Spectrum Microdrive Book by Dr Ian Logan, Melbourne House, can both be recommended. The former contains many useful programs and a list of ROM bugs, the latter was written by the co-author of the ROM and contains a wealth of information.

The newest addition to the range of fast storage devices is the Wafadrive from Rotronics. That is an unashamed attempt to beat the microdrive in terms of the facilities it offers. For the price of £129.99 it offers two drives, Centronics and RS232 ports and, as an introductory offer, a word processing package, Spectral Writer by Softek, which in many ways rivals Tasword II.

On power up the Spectrum behaves as usual until the Wafadrive Operating System (WOS) is called. That is done by entering NEW *, at which point a copyright message is displayed and the system is ready to run. The syntax of the WOS has been well thought out, the normal Spectrum commands are used with the addition of the * to indicate the wafadrive rather than tape in the form:

SAVE *."test"

That applies to all the normal tape commands except DATA. CODE can be made to autorun with the addition of a third parameter. The save name is converted to upper case by the system.

A system of defaults is used so the above line would save to the default drive; if that was the A drive and you wanted to save to the B drive the command:

SAVE *"b:test"

would be used. The default drive can be easily changed using CAT # "b:".

Other useful features are LOAD *, which loads the first program on the wafer, ERASE * "te*" which will erase all programs starting with te and SAVE #"test" which will overwrite an existing program called test. That is useful when developing a program as usually any attempt to save using an existing name will cause an error to protect your programs from accidental erasure. CLS* will reset the ink, paper and border colours to the start up black and white.

It is not possible to save DATA in the usual way. A system of channels and streams, as used on the microdrive, are used with information being PRINTed to it and INPUT back; INKEY$ can also be used. MOVE is used to copy programs from one drive to the other. That will not work with programs which have been protected. FORMAT is used to format a new wafer and also to set the baud rate of the RS232 channel.

When the WOS is initialised it sets aside an area of memory for its own use. That contains a directory of both drives, a 1K buffer into which the sectors of data are loaded and space for the variables used by the system. That takes up 2292 bytes, each additional channel opened takes 1044 bytes and the Centronics interface a further 11 bytes. With so much space taken up, the number of commercial programs which can be easily converted is very small. Fortunately, Rotronics are working on filing and spreadsheet programs for business users and hope to be able to release games in the near future.

Wafers are available in three sizes - 16K, 64K and 128K - and the smaller the capacity the quicker the system will work. Each wafer contains a continuous loop of tape and is designed so that a metal tab protects the tape when the wafer is removed from the drive.

When testing the system for speed a 64K wafer was used, being middle of the range and most useful to 48K Spectrum owners. Formatting the wafer takes 2.10 minutes; 73 sectors are found, one used for the directory leaving 72K available for storage. A maxi- mum of 32 files can be kept on a wafer due to the design of the directory.

Using the test program it takes 14.55 minutes to save, due to the tape doing one complete revolution per save. It also gives an out-of-screen error after 22 saves as the drive prints what it is saving on screen. Loading in sequence takes 14.30 minutes and 14.08 when using a STEP of -1 ; when erasing it also takes 14.08 minutes. If the wildcard facility is used, i.e. ERASE it only takes 29 seconds because the tape only has to make one revolution. It would therefore seem that with a 64K wafer the minimum LOAD/SAVE time is about 30 seconds; a 64K block takes 40 seconds to save.

The manual supplied with the drive is well laid out and informative about the drives but lacking in respect of the ports. Apart from setting the baud rate it does not explain how to alter any parameters when printing. It appears that codes below 32 are not sent, other than 13 and/or 10 except by using CHR$, codes 32 to 164 are sent as normal and all tokens, codes 165 and above, are expanded. That is adequate for most simple printing but some modems require parity and stop bits to be set (or not) on RS232 signals and printers can use differing line feed settings.

Overall the system has much to offer, proving more reliable than microdrive due to the design of the wafers, but the memory usage is very high and its speed slow compared to other available systems. It will probably be popular with business users where reliability is paramount and the Spectral Writer program is a good indication of what can be achieved. It is very similar to Tasword II in operation, whose text files can be loaded directly, with additional features such as page headings and numbers. It is rather quicker although some of the features are not so convenient, it tends to work on the text file globally rather than by paragraphs and so when justifying the file you cannot do so selectively. It can give odd results, as is found when there are two words on a line at the end of a paragraph and the file is justified. The words are moved to the far left and right rather than both to the left margin.

Provided you do not want to convert your own programs or can use the machine code method of using the screen, and you are not worried by the lack of speed then the two drives and ports are very useful. If you use the MOVE command to make back-up copies of wafers be prepared though to take a long coffee break.

Next month we look at some of the floppy disc systems available for the Spectrum. Both 3in and 5 1/4in systems are now available including one which we shall be revealing exclusively and which will raise a few eyebrows. We will also include a table detailing the performance of all the drives now available.

Challenge Sprint, £69.95 from Challenge Research Ltd, 218 High Street, Potters Bar, Hertfordshire.

Sinclair Microdrive Expansion Pack, £99.95 from Sinclair Research, Stanhope Road, Camberley, Surrey.

Wafadrive. £129.99 from Rotronics, Santosh House, Marlborough Trading Estate, West Wycombe Road, High Wycombe, Buckinghamshire HP11 2LB.

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.

COLIN CHRISTMAS GETS iN THE FAST LANE.

HARDWARE

When fast access storage systems for the Spectrum were first introduced to us out here in User Country, everybody who could afford it went for a Drive, Disc or Micro - the members of the new elite would ask one another. What's it like? asked the rest of us taking a knife to the piggy bank.

Once again it seemed that the Spectrum was being raised to new heights. Those cassette recorders suddenly seemed to look quaint and out dated. Serious micro users whether programmers or like myself just users and consumers of software and peripherals that look as though they mean business, recognised the potential of the new hardware.

One of the newest is the ROTRONICS WAFADRIVE. It is an impressive , neat and businesslike unit weighing some 900g and occupying a pride of place 230mm x 110mm x 80mm behind the Spectrum. It is connected to the expansion port by a sturdy ribbon cable. It uses two magnetic tape drives incorporated in the unit and small compact plastic cartridges or wafers, 67 x 45 x 6mm in size. These are available with three nominal capacities of 16K, 64K and 128K.

In practical terms, the 16K wafer is most useful when speedy access to limited amounts of information, small programs, is required, Rather like a pad or notebook, a 'try out area' before the finished data or program needs to be safely filed away and stored for future reference. Here, the other wafers fulfill their most useful function. Location of files on the 64K and 128K wafers or cartridges takes longer of course. Nevertheless with a search speed of 15 inches per second, both drives in the unit offer a maximum or 'worst' access time of 45 seconds using the 128K wafer.

The infinite loop tape (one sixteenth of an inch wide) inside each wafer is completed by a conductive splice which can be 'read' by the Wafadrive System when the drives are operating. LEDs are used to indicate the status of each drive and also when the power is on in the unit. The wafers are not easily damaged, handle well and can have the information stored on them protected in the same way as normal cassettes. The novelty of rapid access, storing and retrieving programs and data, takes a long time to wear off.

The Wafadrive operating system reserves about 2K of the Spectrum's memory for the two drive directories, which hold all the information about the wafers in the drives and the files stored on them. Also for systems variables, some of which can be usefully PEEKed and POKEd and also for the read/write buffers used by the system to hold sections of programs as they are read from or written to the wafers.

EXTENDED BASIC

The operating system also provides the Extended BASIC commands which give access to all the extra facilities of the Wafadrive. Separate interfaces are not necessary with this unit. Rotronics have incorporated both the Centronics and RS232 interfaces and along with the familiar expansion bus, ports for these are located at the rear. This means of course that the Spectrum can then drive any compatible printer. But via the RS232 interface though in many ways unsatisfactorily slow, information can be received say from modems or even other computers.

Finally, a User Manual, a blank wafer and a word processor wafer are supplied with the unit. For those of us who choose to spend a lot of time over a typewriter keyboard producing vast amounts of material which then has to be documented and then filed, this latter is a useful facility which can be used as soon as the Wafadrive is connected up after unpacking. There again, word processor facilities have a special appeal if not function for me in any case. However, after using TASWORD for a long time, it is my opinion that it is hard to beat.

The manual is easy to use for both beginner and expert, young and old alike. I liked its format and size, something like an office file or manuscript itself. More of a Manual than an instruction book. It contains masses of information relating to the straightforward use of the unit but at the same time offers to stretch your knowledge and experience of both the Spectrum and BASIC. Not to mention a lot of useful and well expressed information about how the unit works.

Anyone going for a Drive needs to take this newcomer into account when the day comes.

SMOOTH DRIVES

Carol Brooksbank looks at two utilities for owners of microdrives and wafadrives.

These two programs are designed to make life easier for users of the Spectrum cartridge based storage systems - Wafadrive and Microdrive. The Rotronics Toolkit wafer has a suite of seven Wafadrive programs, some of which have appeared as listings in Rotronics' information sheets. The first gives a screen dump in three sizes on Epson compatible printers (approx. 5.5, 11 and 16.5cm wide). The smaller sizes give slight vertical distortion - a true circle on the dump must be a horizontal ellipse on the screen - but the third gives true proportions. There are programs for sending binary data to the printer so that bit image graphics modes can be used, for enabling the TAB command (usually inoperative with Wafadrive interfaces) and also for letting you specify line length and left margin width. These make the Wafadrive a much more versatile printer interface.

With the Wafadrive initialised, part of the Spectrum memory is lost to its Operating System, and cannot normally be recovered without losing the program from memory. 'De-initialise' lets you do that - an important facility if you are trying to load long programs from wafers. Part of a program can be temporarily stored in the display file, the WOS de-initialised and the program transferred from the screen to its proper place.

The "File Utility' program has nine useful menu options, letting you examine the files on a wafer, change file names without loading and re-saving, or position the tape when saving a multi-file program to achieve minimum load time. The Wafadrive's LOAD * command, which loads the first program on the wafer, requires the first item saved in a multi-file program to be the loader. Since this is frequently the last to be written, it usually means copying the whole thing to another wafer. Now you can move the last file title to the top of the directory so that it is loaded by LOAD *.

The option to change the file type seems to me to be fairly useless, because unless file type and data match, it will not load. It lets the directory show BAK for backup tapes, LST for lists and so on, but I would rather let the file title show this than have to change the directory before it can be loaded. There is a file protection option which protects a file from accidental erasure, but also from the MOVE command which might permit its salvage from a damaged water. It prevents the making of another wafer copy, but not a tape copy, so the protection is not really sufficient to prevent piracy. As a protected program must auto run, and include special commands if the keyboard or the Wafadrive BASIC are to be usable, its value seems limited.

One of the most useful options tries to recover a lost directory, usually caused by switching the power off with the wafer still in the drive. The handbook gives you only a 50% chance of success, but I have a faulty wafer which will only ever load in the drive in which it was formatted, and this utility loaded it in the other drive. Successful directory recovery allows you to save all the files, or, if only part of the directory was recovered, at least some of them can be salvaged. I wish there were also provision for recovering bad sectors, a much more common reason for file loss.

The final program is the 'Transfer Utility', to help in transferring commercial software to wafers. It includes tape header reading, stopping autorun and anti-MERGE so that BASIC can be studied, counting the bytes on a tape file, deinitialising the WOS, and a simple monitor to allow you to examine and modify machine code. Using this program, and the excellent appendix on transferring software, I was at last able to get Psion's Scrabble onto a wafer. There is also provision for making Kempston compatible joysticks operate with the Wafadrive.

Wafadrive Toolkit contains some valuable programs - plus a couple with not much more than novelty value. The second program, M-DOC, is for recovering files from a damaged or faulty Microdrive cartridge.

On loading it presents 15 options, of which the one which scans the whole cartridge collecting sector details must be selected first. If you then opt for a list of all the sectors, each is listed with its number (for used sectors the filename and record number) and a status report: good, bad, missing, unreliable or unused. An unreliable sector, marked when the cartridge was formatted, will not be used, but a bad or missing one will prevent the file from loading, and these are where the program is most useful.

Files, records and sectors can be examined individually, bad sectors identified, and the Microdrive channels examined and modified. Unless you know what a Microdrive channel should consist of, you will need a book about the Microdrive before you can use this vital option. Corrected channel data is put back on the cartridge. Missing records and sectors cannot usually be recovered, but dummy replacements can be made in unused sectors so that the file can be loaded and at least some of it salvaged.

When bad and missing sectors have been replaced it is still probable that the data will have been corrupted, so there is a data filter option. If, for instance, the file is a word processor document, you can set the filter parameters so that non-text bytes are replaced by an asterisk, save it back to the cartridge, load it into the word processor and correct the asterisks. It is possible to correct data using the channel modification option, but easier to use the program which originally created the file. A useful supplementary program checks through BASIC correcting or marking corrupted line numbers. Lines with syntax errors are noted, and heavily corrupted lines changed to REM statements. Each time the program runs one error is marked for line editing, so it can take time to correct a badly corrupted program. When the line numbers and syntax make sense, the program is reported 'ready to edit'. You must then go through it, replacing REM statements which hold the leftovers of corrupted lines, and checking the whole program before saving it again.

This is not a program for the impatient. If you want to recover lost files you must be prepared for painstaking and fiddly work, but the program is effective, provided you either, know how a Microdrive file is constructed or are willing to find out before you start to use it.

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 WAFADRIVE unit consists of a large black box containing two stringy floppy drives, the disk drive interfacing and the serial and Centronics parallel ports. It connects to the Spectrum via its flat cable to the system edge connector. There is a power indicator and each drive has a drive-active LED. At the rear of the unit are located the expansion bus connector and the nonstandard Centronics and serial connectors. Included in the package are two wafers, one blank, the other containing Softek's Spectral Writer word processor.

SYSTEM DESCRIPTION:

The WAFADRIVE belongs to the group of stringy floppy drives. The wafers are ENTREPO stringy floppy cartridges with varying capacities of 16K, 64K or 128K (formatted). As the file storage is sequential, the access time increases linearly depending on the capacity of the cartridge. The access speed is improved with the use of a fast search speed for swift file location. The extended Basic commands made available by the Wafadrive Operating System (WOS) do not come into operation until the system has been initialised with a NEW* command. Once initialised, the WOS reserves about 2K of the Spectrum's memory for its own use. The WOS resides in a special 8K ROM, which is paged automatically like Sinclair's ZX Interface 1 ROM. The WAFADRIVE unit also incorporates a Centronics parallel and a serial RS232 interface, both accessed via the extra ROM commands. Software access to these ports is via the channels and streams procedure known to the ZX Interface 1 owners. The availability of the two ports means you can connect any low-cost printer via the parallel port, while at the same time communicate with another computer system via the serial port. The inclusion of a full-blown word-processing package converts the Spectrum into a 'serious' home or small business computer.

OPERATING SYSTEM:
Extended Basic residing in automatically paged ROM.

SYSTEM COMMANDS:
BREAK aborts execution of Basic.

CAT*"d:" displays the directory of the wafer in the specified drive.

CAT # "d:" loads in the directory of the specified drive without displaying it on screen.

CLEAR* closes all previously opened streams or data file channels and sets streams 0-3 to their default allocation.

CLOSE # stream closes the stream previously opened using OPEN # and sets streams 0-3 to their default value.

CLOSE #* stream closes the stream previously opened using OPEN # or OPEN #*. Closing streams assigned to data file output channels causes the file to be stored on wafer and the directory to be updated.

CLS* clears the screen but also resets the attributes to PAPER 7, BORDER 7 and INK 0.

ERASE*"d:filename" removes the specified file from the wafer. Wild card facility operates with ERASE.

FORMAT*"R"; baudrate sets the RS232 transmit/receive data rate. Default value is 1200 baud.

FORMAT*"d:wafername" formats and names wafer.

INKEY$ # stream; variables reads next single character from previously opened input channel, via assigned stream.

INPUT # stream; variables reads data from previously opened input channel, via assigned stream.

LIST # stream, line lists program, starting at optional line number, to specified stream.

LOAD*"d:filename" loads specified program, Basic or machine code. LOAD* alone loads first program in directory of wafer in default drive.

MERGE*"d:filename" merges specified Basic program with that currently stored in memory.

MOVE*"d:filename1" TO"d:filename2" makes a copy of file specified in filename', optionally giving it the name specified in filename2 Wildcard works with MOVE.

NEW clears Basic program and also resets the WOF, freeing the reserved RAM.

NEW* initialises the WOF, reserving around 2K bytes for the directories and extended system variables.

NEW# clears the Basic program area without resetting the WOF.

OPEN # stream, "channel" opens the specified stream and assigns it to the specified channel.

OPEN#* stream,"port" opens the specified stream and assigns it to the specified port.

OPEN#* stream,"d:filename" opens the specified stream and assigns it to a data file channel. The channel is opened as an output channel, if the file is new, otherwise as an input channel.

PRINT# stream;"string", data, variables sends string or numeric data to previously opened output stream.

SAVE* "d:filename" LINE run saves Basic program in memory to drive specified. Optional LINE suffix gives autorun facility. Error report if file already exists.

SAVE*"d:filename", start, length, run saves machine code bytes from memory. Optional autorun facility. Error report if file already exists.

SAVE# provides same features as above, but allows overwriting of existing file.

VERIFY*"d:filename" verifies Basic or machine code program on wafer against that stored in memory.

ERROR REPORTS:
26 error reports

EXTRA FACILITIES:
Serial RS232 interface with software selectable baud rates from 110 to 19200 baud. Sending and receiving of text and binary files. Centronics parallel output port.

MANUAL:
Excellent 68 page manual with good introductory instructions, full explanation of entire system including parallel and serial port usage, complete command summary, error report list and valuable information for experienced programmers including memory map and port addresses and explanation of extended system variables.

APPLICATION PROGRAMS:
SPECTRAL WRITER word processing package by Softek with 64 character wide display, extensive facilities including printer configuration.

CRITICISM:
Slow access time with high capacity wafers. Non-standard parallel and serial port connectors require specially configured cables.

COMMENTS:
Excellent value for money system offering two drives, Centronics and RS232 ports and useful word processing package. Despite similar performance to ZX microdrives, the drive system has a more rugged and reliable feel. The Wafadrive system doesn't provide local area networking, but has extra parallel port for low-cost printer connection.

MEDIA:
Entrepo stringy floppy wafers with infinite loop 1/16" width various length tape for 16K, 64K and 128K capacity. Write protection by removable tab. Life expectancy approx. 5000 passes.

Prices
16K Wafa £2.49
64K Wafa £2.79
128K Wafa £2.99

TECHNICAL SPECIFICATION:
Number of drives: 2
Storage capacity (formatted) max. 128K
Sector size: 1K bytes
Number of sectors: up to 128
Transfer rate: 18K Baud (2K bytes/sec)
Tape speed: 10"/sec (fast search 15"/sec)

TIMING:
Formatting (approx):
16K 47 secs
64K 2 mins 30 secs
128K 4 mins 42 secs

Cataloguing (approx):
16K up to 8.5 secs
64K up to 27 secs
128K up to 47 secs

Loading a screen (approx):
16K up to 12.5 secs
64K up to 29.5 secs
128K up to 51 secs

PRICE: £129.95

Leads:
Centronics £12.95
RS232 £10.95