Sinclair 128K, by Sinclair???

[Bubu]

Jarl, torpedos!

Hi, all!

I wonder if Sinclair made a computer with 128K. The Spectrum +2 models, as we all know, weren't made by Sinclair, but by Amstrad. And the Spectrum+ 128K (toastrack) not sure if it was made by Investronica (Spain)

Does anybody know about that?

[Rorthron]

QL

[Bubu]

Ah, that's true

And with a Z80 inside, and 128K?

[Rorthron]

And with a Z80 inside, and 128K?

No. The ZX Spectrum 128K was developed, as you say, by Investronica.

[1024MAK]

The ZX Spectrum 128K was developed by Investronica in cooperation with Sinclair. The Spanish version was developed and released first.

In the U.K., as Sinclair had a very large stock of ZX Spectrum + models, the U.K. version of the ZX Spectrum 128K was released later. But it was definitely released as a U.K. design (there are some minor differences on the PCB). At least some of the U.K. model were made in the U.K. (maybe all).

Then Sinclair accepted the offer from Amstrad. At first Amstrad continued production of the ZX Spectrum 128K. We don’t know for certain, but production of the ZX Spectrum + may have already stopped (Sinclair still had a very large stock of these on the date of the sale to Amstrad). Production of the QL had also stopped.

The circuitry of the ZX Spectrum +2 (grey) is very closely based on that of the ZX Spectrum 128K and the Interface 2. The ZX Spectrum +2A, ZX Spectrum +3 are a new hardware design. Some ZX Spectrum +2 (grey) machines were made in the U.K.

So if the question is, did Sinclair Research Limited release a U.K. computer with 128K of RAM, the answer is yes. Both the QL and the ZX Spectrum 128K.

Mark

[Bubu]

Then the toastrack (Zx Spectrum+ 128K) was made by Sir Clive Sinclair, in England. OK, that's the thing, as I wanted to test every Sinclar computer, but not interested in Amstrad. I won some Zx81, Zx Spectrum 16K, Zx Spectrum 48K, Zx Spectrum+, and a QL. But I still haven't tested the Zx80 and the Zx Spectrum+ 128K. I'm prepairing my wallet...

And a tech question: if I wanted to program a game for the Zx Spectrum+ 128K, how cuould I access to the address 10000 e.g.? Are there 2 memory banks?

[ZXDunny]

Then the toastrack (Zx Spectrum+ 128K) was made by Sir Clive Sinclair, in England. OK, that's the thing, as I wanted to test every Sinclar computer, but not interested in Amstrad. I won some Zx81, Zx Spectrum 16K, Zx Spectrum 48K, Zx Spectrum+, and a QL. But I still haven't tested the Zx80 and the Zx Spectrum+ 128K. I'm prepairing my wallet...

And a tech question: if I wanted to program a game for the Zx Spectrum+ 128K, how cuould I access to the address 10000 e.g.? Are there 2 memory banks?

There's a port you OUT to that switches memory banks in and out.

[Bubu]

And I understand that that port has an odd number, hasn't it?

Do you think that this Spectrum+ 128K model is 100% compatible with 48K games? if I do an out(254), a to make beeps, does it work in the 128K model?

[AndyC]

100%, no. But 99.9%, yeah probably.

[ZXDunny]

If you specify which spectrum you're developing for, people will switch their emulators accordingly.

[Bubu]

If you specify which spectrum you're developing for, people will switch their emulators accordingly.

I like developing for real machines, better than emulators, but I don't own any toastrack, so I have to test my games with emulators, but don't know what test should I do, as I don't know where is that incompat

[ZXDunny]

If you specify which spectrum you're developing for, people will switch their emulators accordingly.

I like developing for real machines, better than emulators, but I don't own any toastrack, so I have to test my games with emulators, but don't know what test should I do, as I don't know where is that incompat

Then just don't develop for the 128k? If using an emulator is sinful and ideologically unsound for you then there's no shame in just saying "I developed this for the 48k".

[AndyC]

If you develop for the 48K, use standard port numbers for OUTs, avoid the floating bus, avoid cycle precise timing and avoid relying on specific bytes appearing in the ROM, you'll almost certainly be fine.

And that's pretty extreme as most ROMs have key routines fixed in the same places etc, but you'll maximize compatibility if you don't count on it. Likewise many other subtle differences can be worked around if needed (even the floating bus can be handled on -2A/+3 machines these days!)

Worst comes to worst, it'll only run on a 48K machine. And so people will just use a 48K or suitable emulator. Or someone will release a patch that fixes it.

[Bubu]

If you develop for the 48K, use standard port numbers for OUTs, avoid the floating bus, avoid cycle precise timing and avoid relying on specific bytes appearing in the ROM, you'll almost certainly be fine.

Nice, I use standard ports, no cycle precise timings, and nothing to the ROM routines. I don't know what is the floating bus. But I'll read about it.



I only wanted to put a stamp on my tapes, regarding this: compatible with all models of Sinclair Spectrum (more than 16K).

Thanx a lot, @AndyC

[AndyC]

I only wanted to put a stamp on my tapes, regarding this: compatible with all models of Sinclair Spectrum (more than 16K).

Well you can also always just ask around, there's bound to be someone with an actual 128 who can try it out

[Joefish]

Just develop on real 48K hardware, and use emulators set to 128K and +2A modes to test it doesn't fail horribly. That covers most machines for compatibility.

The original Sinclair Toastrack 128K machine, the Amstrad-made Grey +2 and Spanish 128K machines are pretty much identical right down to the hardware. Only the Black Amstrad +2A got a re-design, and again that's almost the same machine as the +3 (apart from the tape instead of the hard drive). There are a few fiddly compatibility issues between the +2 and the +2A generations, but very unlikely anything that will make a difference to you developing a 48K game.

Many emulators will also emulate some Russian clone machines, but those have all sorts of incompatibilities and timing differences, so I wouldn't worry about those.

Of course every reviewer who looks at your game now will whine like a baby and mark you down because it doesn't have grating 128K elevator music playing incessantly throughout the game, but then they're not all right in the head anyway...

[1024MAK]

The “floating bus” is the value on the data bus read by the Z80 when there is no device intentionally driving it.
In all models that have 48K or more of RAM, there should never be any memory address where this happens.

However, with Z80 input/output ports, because on an unexpanded machine there are many I/O addresses that are unused, if the Z80 reads (via the IN instruction) from an address where there is no I/O device to drive the data bus, the Z80 will actually read either the value 255 (due to nothing driving the bus and each data line going to logic high) or the value of screen data that the ULA is reading from the “lower” RAM. Although never a documented feature, some programmers discovered this affect and used it to synchronise the timing of their machine code to the actual ULA display operation.

That’s fine on all the Sinclair ZX Spectrum models, but not for the Amstrad +2A, +2B, +3 or +3B, which use different circuitry (they use a gate array rather than resistors and a ULA). These Amstrad models therefore will not correctly run games that use the “floating bus” affect.

Mark

[Bubu]

Great answers, @Joefish & @1024MAK !! Thank both!!

And (yet another) question about the 128K toastrack: I've seen some emulators with English version of that computer, but does anybody know wich emulator does it with the Spanish (Investronica) version?

[druellan]

Try Es.pectrum from Habisoft http://www.habisoft.com/espectrum/EN.htm I think it has the ROM. It is also a very competent emulator to have around.

[Bubu]

[Alessandro]

Retro Virtual Machine, SpecIDE, ZesarUX and FBZX also emulate the Sinclair/Investronica Spectrum 128 natively.

Several other emulators will emulate it too, by replacing the Sinclair 128 ROM with that of the Sinclair/Investronica, or by selecting the latter as custom ROM for that model (e.g. Spectaculator).

[PeterJ]

We list the emulators that do on my emulator sheet. Do PM me with any errors or omissions.

app.php/emulator-comparison-spreadsheet

[Bubu]

OK, I think SpecIDE and FBZX are missing in that Excel.

And I would add a very important info: free? poundware? ...