Open Source, DIY 512KB RAM Expansion

revaldinho · 12:44, 25 May 22

Quote from: aerobaticant on 09:25, 25 May 22Hi @revaldinho, and everyone. I have succesfully created a DIY version of the universal RAM expansion board on prototype PAD board! I changed the JTAG header to be a single in-line pin strip as this it what I have used on other projects using Xilinx devices.

I used an XC9536-15PC44 as I have a few lying around. Looking at the code, and using a 55ns SRAM, I couldn't see a reason why this shouldn't work, unless I've overlooked something important.

Looks great!

You must be a bit of a masochist to build on perf-board, because the project PCBs are easily sourced from many places and also can be had directly from Seeed. Still, it's a nice job. The point to point wiring looks very neat.

Your XC9536-15PC44 should be fine. All the speed grades for the XC9500s should work with all my projects. Even the slowest 15ns ones are way faster than the original LS TTL would have been.

Quote from: aerobaticant on 09:25, 25 May 22Any suggestions of some good (6128?) games to try?

I think the Batman Forever demo is the first thing to try - assuming that you have the 'right' CRTC

aerobaticant · 14:32, 25 May 22

I agree - there was a bit of masochism, but there's motive in my madness.

I am considering creating an updated version with a schematic (already drawn in KiCad

) and using a newer CPLD.
The Atmel/Microchip ATF15xx family looks to be about the only option currently in production.
I'd also consider moving to an SMD version of the SRAM IC.

Any thoughts?

revaldinho · 14:57, 25 May 22

Yes, the ATF15xx seems like the only 5V compatible part available now, so it's a good choice. I have thought of porting some projects to it but haven't got round to it. The tool chain for Verilog looks a bit more convoluted than the Xilinx one.

As to whether to SMD or not, I just preferred to stick to through hole components to make my projects easy for anyone to build. My more recent projects are mainly using just 74 series parts to avoid the need for any programming equipment altogether as well as being easy to solder. And they are very retro! The 512Kx8 is the largest SRAM available in through-hole though, so if wanting to do the 1MB or a larger card then I can see it makes some sense to move to SMD for that, where you can get the larger capacities in a single chip.

Rabs · 17:39, 26 May 22

Hi, @revaldinho , just to say thanks again for the 512k old school ram expansion pack project. It worked

and I now have a fully functioning 512k ram expansion.

Learnt a lot along the way.

Any recommendations on what next to try?

revaldinho · 20:36, 26 May 22

Quote from: Rabs55 on 17:39, 26 May 22Hi, @revaldinho , just to say thanks again for the 512k old school ram expansion pack project. It worked and I now have a fully functioning 512k ram expansion.

Learnt a lot along the way.

Any recommendations on what next to try?

Always good to hear about people building these projects for themselves.

If you want to build another in the same vein, then the EightROM is all 74 series too but you do need to be able to program your own (E)EPROMs or get hold of them pre-programmed from somewhere else.

The project I want to recommend though is the CPC-CPLink card. Again it's all 74 series, so another easy build. It allows you to plug a Raspberry Pi right into the back of the CPC as a co-processor. Possibilities for expanding the CPC via the RPi are enormous and should offer a lot of coding fun. Since the CPlink card takes care of all the interface timing you can code in whatever language you like on the Pi. For example, @biged & I created a very simple GPU application providing the CPC with a second screen using BBC BASIC - see the latest posts in this thread and the screenshot attached showing the CPC output in a window on the Pi (full screen mode is possible too).

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Rabs · 21:16, 26 May 22

Great thanks, both projects look interesting.

Rabs · 11:17, 21 July 22

Finally worked out how to upload images.

Here is my trio of cards, the CPC-CPLINK (and just look at the size of the PI model B on the back), the Eightrom card and Old School 512k RAM expansion. All working.

I highly recommend these projects to anybody thinking about building them, the information and support is excellent. I have very little prior experience and found the projects challenging but fun and I have learnt so much along the way.
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netmercer · 00:01, 25 November 22

Hi,
I'd like to buy a Universal CPC 512K RAM Card (the version with CPLD XC9536), which was developed by revaldinho.
Either a bare PCB or a complet card would be fine, regardless of which. Perhaps someone wants to sell such a device.

Best regards from Germany
netmercer

Rabs · 09:28, 25 November 22

Quote from: netmercer on 00:01, 25 November 22Hi,
I'd like to buy a Universal CPC 512K RAM Card (the version with CPLD XC9536), which was developed by revaldinho.
Either a bare PCB or a complet card would be fine, regardless of which. Perhaps someone wants to sell such a device.

Best regards from Germany
netmercer

Hi, I could try and send you one of my spare PCBs from the UK, see my post in the classifieds.

Message me if interested.

revaldinho · 12:12, 25 November 22

Quote from: netmercer on 00:01, 25 November 22Hi,
I'd like to buy a Universal CPC 512K RAM Card (the version with CPLD XC9536), which was developed by revaldinho.
Either a bare PCB or a complet card would be fine, regardless of which. Perhaps someone wants to sell such a device.

Best regards from Germany
netmercer

If you're happy to build your own then please go ahead and take up Rob's offer for one of his spare PCBs.

I still build all my projects to order for CPCWiki members, and often make up one or two extras when I do. Right now I have one 512K universal card built and tested. So if you prefer the ready assembled option that would be £22 for the card and £9 for tracked postage to Germany. PM me for details.

Rev.

GUNHED · 16:06, 25 November 22

Quote from: Rabs on 11:17, 21 July 22Finally worked out how to upload images.

Here is my trio of cards, the CPC-CPLINK (and just look at the size of the PI model B on the back), the Eightrom card and Old School 512k RAM expansion. All working.

I highly recommend these projects to anybody thinking about building them, the information and support is excellent. I have very little prior experience and found the projects challenging but fun and I have learnt so much along the way.
You cannot view this attachment.

Wow! This really looks awesome!!!
Well, I also think about getting the CPC-CPLINK one day. How do you like it?

revaldinho · 17:47, 25 November 22

Well, if you'd like one I have at least one of those built up too - same deal as the RAM card £22 for the card + £9 for tracked postage to Germany. Pi ZeroW or Pi3A+ cards fit nicely on the back, but getting hold of those is a bit more problematic these days.

darkhalf · 08:14, 27 January 23

QuoteXC9536-15PC44 should be fine. All the speed grades for the XC9500s should work with all my projects

Unfortunately the only active Xilinx these days are the XL 3.3V series and those are in SMD versions. We use the XC9536XL on our Nistune automotive computer boards, but use a 3.3V drop down regulator to make them work with the 5V power. The IO on these still work with 5V ranges, which is good.

You would need to rebuild the project to generate XL version JED files for programming with ISE (which is another story, since the Win10 doesn't support it)

I've had very mixed success lately with the older 5V XC9536 versions, with about half DOA or failing to program