Spectrum +3 differences.

[Bryce]

I recently (this week) got my first Speccy +3 and have just started investigating its Hardware. I was hoping to document the differences to see which of my hardware projects would work on it. But I haven't had a chance to take a detailed look yet.

Here's some of what I found so far:

- The expansion port is completely different. So sorry, the MegaFlash wouldn't work without major changes.
- With the correct cable, my S-Video modulator works great.
- The disc-drive is CPC compatible, ie: it will read and write CPC discs without a problem.
- The Drive B port is an exact copy of the UK 6128 - Edge connector with same pinout. I connected my HxC to it and it works fine. (I now have a flat-cable from the HxC with three connectors on the end which allows you to connect to 4 different computers: UK CPC6128, DE CPC6128, 6128 Plus and Speccy +3 ) I haven't added an ABBA switch yet, but that will come later.

- Printer port is 8-Bit (and sadly also only usable as outputs).
- The disc controller is a µP765 just like the CPC. It uses an SED9420 Data seperator.
- The AY-3-8912 is used slightly differently. It controls RS232 and Keypad sockets instead of the keyboard. The keyboard is being read directly by the Gate Array.
- It has 2x 256K ROMs (unlike the CPCs).
- The RAM are 64Kx4bit ICs
- CRTC stuff is performed by the Gate Array and the TV output is being driven by a TEA2000 which tends to give a better picture than the MP1/2 1377 did. They also implemented a real delay line, which the MP1/2 skimped on.
- They were nice enough to give it a reset switch, but forgot to give it a power button.
- The PSU supplies +5V, +12V and -12V (which could allow very interesting internal expansions)

Bryce.

[Bryce]

Quick question: How many CPCs owners actually own a Spectrum +3 and would like to use their CPC stuff on the Speccy too?

Bryce.

[redbox]

Quick question: How many CPCs owners actually own a Spectrum +3 and would like to use their CPC stuff on the Speccy too?

I don't have any Speccys and if I got one I'd expect it would be the 48k rubber key one purely for the retro-ness of it 

[Bryce]

Yup, have a 48K too. It was thrashed when I got it, but you can see its "resurrection" here: http://www.cpcwiki.eu/forum/index.php?topic=2450.msg26308#msg26308

The 48K Speccy is a completely different machine (has the same expansion port as the +3 though), so no CPC hardware has a chance of working on it.

Bryce.

[SyX]

Bryce, take a look to the page of Cristian Secara, he has a few fixes for the +3 bugs, how the problem with the sound in the first revision of he +3, he has software and another interesting things for the +3. Another interesting pages are Gary Lancaster's +3e and Sami Veemah, one of the best "ZX Bryce" clones , nothing how the original, of course 

[Bryce]

I was aware of the AY bug, but I didn't test whether my one has it yet. Mine is an Issue 1, so I assume it probably does need this fix. The ROM fixes I've found, seem to fix a minor bug, but introduce a more significant bug, so I don't think I'll bother making that change.

I'd seen the +3e page, his IDE interface is absolutely brilliant, that's what I call minimalistic hardware! I might make an internal version of this with CF card, but with the HxC working, I don't really need it urgently.

I didn't know Sami Veemahs site, so guess what I'm reading now

WorldofSpectrum is also very good. A huge selection of DSKs can be found there too.

Bryce.

Edit: Where are these people getting all those expansion connectors from? I thought they would be even rarer than out precious 50way edge connector?

[SyX]

The Sami's projects are really nice

Edit: Where are these people getting all those expansion connectors from? I thought they would be even rarer than out precious 50way edge connector?

I don't have any idea, we'll need to ask them, jejeje.

[Jase]

Quick question: How many CPCs owners actually own a Spectrum +3 and would like to use their CPC stuff on the Speccy too?

Bryce.

The only one I share between them is an external 3.5" floppy drive.
However with the right adapter, a +3 PSU can easily power an Amstrad CPC6128...

[Jase]

I was aware of the AY bug, but I didn't test whether my one has it yet. Mine is an Issue 1, so I assume it probably does need this fix.

There are many AY bug fixes, but I haven't found one that does the job properly

[Bryce]

Hey, using the PSU for the CPCs is a really good idea! I must make myself an adapter, then my PC PSU can go into storage/retirement

Bryce.

[Jase]

Hey, using the PSU for the CPCs is a really good idea! I must make myself an adapter, then my PC PSU can go into storage/retirement

Bryce.

Just goes to show you what you can learn by reading a website called CPCWiki
http://www.cpcwiki.eu/index.php/Powering_a_CPC_6128_from_a_Sinclar_Spectrum_%2B3_PSU

[robcfg]

I do have a couple of 48k spectrums, a +2 (the gray one) and a +3.


Despite being a Spectrum, the +3 is a nice machine. I haven't tried my external 3.5" drive with the +3, but it should work.

[TFM]

Quick question: How many CPCs owners actually own a Spectrum +3 and would like to use their CPC stuff on the Speccy too?

Bryce.

Well, I don't have one. But why convert software? Wouldn't it be a "downgrade"?

[Bryce]

No idea, I was talking about hardware that would work on both CPC and Speccy.

Bryce.

[dragon]

I buy the zx spectrum ula book,When the book arrive,I see if it speak about the modifications of amstrad to the ula in laters models.



Maybe the book can help you bryce.


An stupidy question.if the amstrad and the spectrum shares de microprocessor.Is posible produce an expasion card that the amstrad can work in spectrum mode?

[Bryce]

An interesting idea, I didn't check the ULA compatibility, although I assume they are the same or very similar. Like the later CPCs, the Spectrum + replaced much of the discrete functionality with an ASIC, so it's hard to tell. Let me know what the book says.

CPC Spectrum Mode: I doubt this would be easily achievable. It would need a modified ROM that re-routed all the Spectrum addresses to the CPC equivalent and many many other modifications.

If you really want that Spectrum look and feel on your CPC, just load up Black Tiger, cover the speaker with Tin-foil and smear the monitor with grease (for that subtle blurred effect). Viola, your very own Spectrum Mode

Bryce.

[dragon]

mmm.I not sure if all ulas in spectrum are the same.For example when investronica design the spanish spectrum.They use a different ula(texas instruments instead ferranti ula).

And this spectrum has incompatibilities with external peripherals(divIDe for example).

So amstrad might have touched something in ula of later spectrums.(I read spectrum +3 lost several signals in expansion port,but i not know if this signals are controlled by the ula.If they are controlled by ula and eliminated.Amstrad probably modified the ula somehow.)

[Bryce]

I think the DivIDE incompatibilities were due to the new RAM addressing, which was implemented to allow CPM to run, but I'm not sure.

Bryce.

Edit: Oops, I meant on the Spectrum +, not on the Investronica.

[MacDeath]

CPC Spectrum Mode: I doubt this would be easily achievable. It would need a modified ROM that re-routed all the Spectrum addresses to the CPC equivalent and many many other modifications.

would need a complete additionnal ASIC I guess, the sort of the PLUS Asic but designed to get a Speccy emulation instead of a CPC emulation.
Basically it would be like to get a CPC and a Speccy on the same motherboard, with a possibility to switch between both modes/Roms at some point.

CPC can get a Mode1 256x192 resolution, but it can't get a 1bpp square pixel screen with this and also definitely lacks the Attributes.

but if CPC could get a downgraded Mode2 with Mode1 pixels perhaps...


Yet what would be the point ? beside getting at last accurate speccy ports ?


Thomson 2nd generation 8bit computers were great in that they cumulated the Amstrad PLUS modes (minus the Hardware sprites/Scrools) and a 4th Attributed mode, but this one is more compairable to MSX1 video mode : 320x200xattributes : 16 colours on screen and 8x1 attributes...

While such 1bpp bitmap is quite Speccy like, the attribute grid is 8 time what's on speccy (8x1 instead or 8x8 attributes) and also the 320x200 instead of 256x192 also increase the weight.

perhaps an external stuffyou would plug the Video out on could do the trick... sort of...
Then the CPC would run on... reduced Mode2... (256x192... less than an half screen) and the card would perhaps do the resize/timing stuff, and manage some Attributes managed through the extension port...


Fairly too much work for an actual downgrade of CPC's graphical capabilities.
with at best marginal compatibility...
Hell even "real" Speccys from Amstrad are not entirely "Speccy compatible"...



A modern "1chip computer "Clone could on the other hand offer such crossed compatibilities...



But to be fair, Amstrad PLUS done well would have had 2 ASICs and manage retrocompatibility with both Speccy and CPC, and even with old PCW...

In addition to being an even better PLUS.
Would be quite so Awesome..

[SyX]

mmm.I not sure if all ulas in spectrum are the same.For example when investronica design the spanish spectrum.They use a different ula(texas instruments instead ferranti ula).

And this spectrum has incompatibilities with external peripherals(divIDe for example).

Ooooohhhhh, the looovelyyyy Inves+ , that wonderful computer where the sound output is via mic instead of ear (between other great "features" xDDDD) and that you can destroy the ula with a few pokes... shhhh, i didn't said anything xDDDDD

[dragon]

Ooooohhhhh, the looovelyyyy Inves+ , that wonderful computer where the sound output is via mic instead of ear (between other great "features" xDDDD) and that you can destroy the ula with a few pokes... shhhh, i didn't said anything xDDDDD

Oh I can imagine a james bond game in investronica spectrum. "james,This message will self-destruct in 5 seconds".

5 segundos later

poke.Ula is destroyed go to the shop,buy another spectrum and retry the game.(entirely realistic.) .

Macdeath,I thought more in expansion card with asic,with the ula incorporated(and other necessary stuff).So when you plug the spectrum card in the expansion port the z80 uses de alu incorporated in the expansion card  to load spectrum software.

The spectrum can accept expansions card with ay chip.The amstrad can't accept expansion cards with other chips?

[Bryce]

Yes, the CPC can have any chip you want on the expansion port, but the address range available on the expansion bus (like any 8-Bit) is limited. So connecting an entire ASIC would be difficult, expensive and slow.

Bryce.

[SyX]

And the bandwith is limited too by the CPC hardware design and the bus sharing with the Gate Array/CRTC (CPC's dynamic duo  ), that is because is very difficult or impossible to implement peripherals with DMA access in the CPC, don't you think Bryce? (or i'm specially "tonto" today by the Scarlett's pictures )

Medium OT: By the way Bryce, have you seen the cartridge Harmony for the Atari 2600? There is a few demos that use the ARM microcontroller inside the cartridge how an ARM coprocessor for the 2600, really interesting project 

[TFM]

No idea, I was talking about hardware that would work on both CPC and Speccy.

Bryce.

OMG! Speccy Software ports are cruel! Please don't make the same mistake in Hardware now.
It would be way better to focus on one system (CPC here) and get the maximum out of this IMHO.

[robcfg]

And also unleash the full potential of the Plus range!