Amstrad CPC Plus / GX4000 Core?

[pepito]

Hey!

I'm wonder if this core is in dev?
I saw nothing about CPC PLUS or GX4000 Core.

I know, there are few games and demos available on PLUS only, but some are very good.

[JasonA]

There is a custom Amstrad ASIC in the GX4000 with 100+ pins to wire up. It might be a bit of work to get that ASIC coded.

I havent seen any code on the internet for this ASIC in Verilog or VHDL. If there was, it would save quite a bit of time to complete a GX4000 core.

[pepito]

Once ASIC fully detailed, this core can be built, right?

[JasonA]

I believe so

[NinjaWarrior]

A CPC Plus core will boost new developments for sure, I hope it can be doable in near future crosses fingers

[DakotaCat]

I know this is an old thread but my 2 cents...

Fundamentally, the ASIC in the GX4000 is an extended version of the 40007 or 40010 Gate Array ICs used in the Amstrad CPC. It integrates RAM bank switching, the Programmable Peripheral Interface, some disk access functions, keyboard scanning (50% as the rest is done by the sound chip), Cathode Ray Tube Controller and the extended graphics features; Enhanced Pallet, Hardware Sprites, Sprite Scaling, Hardware Scrolling and DMA sound. Also cartridge security features, though, these could be skipped in a FPGA implementation.

As everything other than the graphics enhancements have already been implemented in the CPC core, theoretically, all that would need to be implemented would be the enhancements, not every pin on the ASIC. Off the top of my head, I'm pretty sure the magic happens 100% inside the ASIC, so the enhanced features wouldn't require a huge amount of reworking as far as I understand it.

I don't have the skills to implement this myself, but I may take a look at it one day when I'm feeling brave. But I think it would be relatively trivial for a skilled core designer to bolt the necessary features on to the vanilla CPC core.

[Moondandy]

That's some great insight there, it would be really nice to get a CPC+/GX4000 core. With there being so many PC and older console cores now, this one is starting to look more and more like an omission. Some decent stuff on there.

[DakotaCat]

Thanks! I have a real soft spot for the Amstrad machines and the Plus/GX4000 machines are actually very capable. There's a lot of homebrews appearing that make use of the enhanced features, there are even some enhanced oldskool titles that have been spruced up with the enhanced palette.

The version of Sonic the Hedgehog in the works shows that the machines were full of potential in the right hands. It's a real shame that the machines didn't take off commercially.

I think a decent FPGA implementation would probably give the scene a real shot in the arm and more people could experience the machine recreated in hardware. Emulation is great, but seeing the transistors do their thing is always magical. This is why I'm so enthusiastic about the Mister.

In theory the enhanced features could be added to a stock CPC, you would just need to implement them, perhaps in CPLD or FPGA. The chips that have been consolidated in to the ASIC on the GX4000 are all there in discreet form. You would have to catch the calls to the enhancements but really from there, it's just writing to RAM essentially.

It's maybe been 10 years since I looked at the Plus/GX4000 documentation, so I'm lacking some of the specifics, but in broad terms I think my thoughts are fairly accurate.

[reno]

Another vote here for an Amstrad Plus / GX4000 core !

IMHO it's one of the most important systems still missing in MiSTer, with a very active homebrew scene in recent years (look at this new game announced this week : https://www.youtube.com/watch?v=bgR8eRgSESI)

And, what other 8-bit system can do this, seriously ?
https://www.youtube.com/watch?v=6VJDowxFwLA

Currently there are at least 2 emulators that support the Plus / GX4000 very well : RetroVirtualMachine and CPCEC (https://github.com/cpcitor/cpcec) which is open source.

[breiztiger]

And caprice forever, sugarbox, ace, winape, mame …

[pepito]

and still nothing on Mister

[breiztiger]

sorgelig said if we have a crtc 3 decap ...

[limi]

And, what other 8-bit system can do this, seriously ?
https://www.youtube.com/watch?v=6VJDowxFwLA

PC Engine would like a word

(of course, its “GPU” is 16-bit, but the system is 8-bit)

[RockRiver]

ASIC 40489 (capa de metal)

https://mega.nz/file/YhU0UKiK#C00ok3jbo ... ixsiKj3C3E

ASIC 40489 (capa base)

https://mega.nz/file/hosFkZpB#Xh71OOcXp ... oFXwAjVFkY

Chip ACID 40908

https://mega.nz/file/Nl0E0JJI#8Sofxqhle ... I7b4qu-QLc

[RockRiver]

Thanks to Robcfg and zonadepruebas people

https://www.zonadepruebas.com/viewtopic.php?t=7651

[emuola]

This awesome news

[FPGA64]

That set of posts was from 2016.

[emuola]

That set of posts was from 2016.

Oh, sorry gor a bit carried away

[RockRiver]

That set of posts was from 2016.

But since 2016 people only did flashcart/"everdrive" with fpga and ACID , nothing with decapped ASIC/crtc

[reno]

sorgelig said if we have a crtc 3 decap ...

Do we really have decaps for all the cores in MiSTer ?

We have a 284 page book detailing all Amstrad CRTCs : http://logon.system.free.fr/down/ACCC1.6-EN.pdf

I hope it can count for something

[emuola]

We have a 284 page book detailing all Amstrad CRTCs : http://logon.system.free.fr/down/ACCC1.6-EN.pdf

I hope it can count for something

I'd also think so

[RockRiver]

Gx4000 / CPC+ vs MSX2
Not so complicated as MSX2/MSXturboR, I think

GX4128 with 128k RAM will be great core.
Incoming hundreds games of CPR files from classic (cpc) and new palette colors and dma music (cpc+)

[breiztiger]

gx4000 is a 6128 plus without keyboard / floppy and only 64k

[reno]

gx4000 is a 6128 plus without keyboard / floppy and only 64k

Or a 464 Plus without tape, and only one key : P for pause

[breiztiger]

https://k3pi.chickenkiller.com/dzi/acid2.html

[pepito]

nice picture!