Amstrad CPC Plus / GX4000 Core?

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Amstrad CPC Plus / GX4000 Core?

Unread post by 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. :D

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Re: Amstrad CPC Plus / GX4000 Core?

Unread post by 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.

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Re: Amstrad CPC Plus / GX4000 Core?

Unread post by pepito »

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

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Re: Amstrad CPC Plus / GX4000 Core?

Unread post by JasonA »

I believe so

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Re: Amstrad CPC Plus / GX4000 Core?

Unread post by NinjaWarrior »

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

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Re: Amstrad CPC Plus / GX4000 Core?

Unread post by 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.

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Re: Amstrad CPC Plus / GX4000 Core?

Unread post by 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.

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Re: Amstrad CPC Plus / GX4000 Core?

Unread post by 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.

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Re: Amstrad CPC Plus / GX4000 Core?

Unread post by 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.

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Re: Amstrad CPC Plus / GX4000 Core?

Unread post by breiztiger »

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

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Re: Amstrad CPC Plus / GX4000 Core?

Unread post by pepito »

and still nothing on Mister :(

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Re: Amstrad CPC Plus / GX4000 Core?

Unread post by breiztiger »

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

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Re: Amstrad CPC Plus / GX4000 Core?

Unread post by limi »

reno wrote: Fri Sep 08, 2023 5:46 pm

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)

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Re: Amstrad CPC Plus / GX4000 Core?

Unread post by RockRiver »

Thanks to Robcfg and zonadepruebas people

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

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Re: Amstrad CPC Plus / GX4000 Core?

Unread post by emuola »

This awesome news 💪

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Re: Amstrad CPC Plus / GX4000 Core?

Unread post by FPGA64 »

That set of posts was from 2016.

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Re: Amstrad CPC Plus / GX4000 Core?

Unread post by emuola »

FPGA64 wrote: Thu Oct 05, 2023 8:32 pm

That set of posts was from 2016.

Oh, sorry gor a bit carried away 🫣

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Re: Amstrad CPC Plus / GX4000 Core?

Unread post by RockRiver »

FPGA64 wrote: Thu Oct 05, 2023 8:32 pm

That set of posts was from 2016.

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

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Re: Amstrad CPC Plus / GX4000 Core?

Unread post by reno »

breiztiger wrote: Sun Sep 24, 2023 8:35 am

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 :D

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Re: Amstrad CPC Plus / GX4000 Core?

Unread post by emuola »

reno wrote: Mon Oct 09, 2023 4:49 pm

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 :D

I'd also think so :D

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Re: Amstrad CPC Plus / GX4000 Core?

Unread post by 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+)

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Re: Amstrad CPC Plus / GX4000 Core?

Unread post by breiztiger »

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

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Re: Amstrad CPC Plus / GX4000 Core?

Unread post by reno »

breiztiger wrote: Sat Feb 17, 2024 1:21 pm

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

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

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Re: Amstrad CPC Plus / GX4000 Core?

Unread post by breiztiger »

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