Open Source, DIY 512KB RAM Expansion

Started by revaldinho, 00:10, 25 April 18

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revaldinho

Quote from: Animalgril987 on 21:50, 25 January 21Ps. Do you know what the correct DIP switch settings on the memory card will be for my setup?



See quick reference card attached.


All the other documentation is on the project wiki.




Animalgril987

I'm afraid that my ram card appears to be dead. Toto's ram test shows 0k CPU ram.
I gave the CPC edge connector a good clean and used a multimeter to check continuity from the CPC traces to the through connector on the backplane ( all lines were good).
So I connected everything up, and it doesn't look like it's working.

Skunkfish

Hi Alan, I'm sorry to hear that!

Is the switch on the backplane card set to CPC or PSU? This should be CPC if there's no PSU connected to the card directly.

Also, have you tried connecting the card directly to the cable rather than via the backplane card? Is the result any different?
An expanding array of hardware available at www.cpcstore.co.uk (and issue 3 of CPC Fanzine!)

Animalgril987

I'll try giving the CPC edge another clean. If that doesn't work, I'll try directly connecting the card to cable.
I've tried switch set to CPC and using an external psu ( with switch set to psu).


Alan

TotO

Quote from: Animalgril987 on 18:39, 30 January 21
I'm afraid that my ram card appears to be dead. Toto's ram test shows 0k CPU ram.
Please, contact me by email to see how I can solve your problem. :)
"You make one mistake in your life and the internet will never let you live it down" (Keith Goodyer)

revaldinho

#130
Quote from: Animalgril987 on 18:39, 30 January 21I'm afraid that my ram card appears to be dead. Toto's ram test shows 0k CPU ram.

If the RAM test shows 0K CPU RAM, is there a possibility that you made an error in typing the program in ?

[EDIT - removed incorrect results for a '464' which would return 0K. Yes, the unexpanded 464 would indeed return CPU RAM: 0K ]

One thing I would check on the board, since you mentioned you had a multimeter, would be the supply voltage. Take a reading from the RAM pins - bottom left is ground, top right should be +5V.

Beyond that, if it is a hardware failure then the vendor (@skunkfish) should have the opportunity to put things right for you.



Animalgril987

Thanks everyone for all suggestions. Yes it would appear to have still been some grime on one of the edge contacts.


All is good! Toto's ram test shows 448k CPU ram ( 464 in full C3 shadow) with both CPC power and external psu.


Alan


;D ;D

revaldinho

That's great! You should get the full 512K RAM in DK'tronics mode and for most software that will be fine. FutureOS is on of the very few programs which needs the shadow mode.


(BTW, Sorry I was wrong with the CPU RAM report - I tried that program on a a 6128 and of course it did report CPU RAM 64K since it has the extra bank built-in.  :picard: On a stock 464 it would return 0K. Unfortunately my DDI-3 isn't working with my own '464 to load the program on that at the moment. May well be more edge connector problems...)


SerErris

@revaldinho


I am going to build an eightrom today, but thinking of the following question.

Would it be possible to setup a GAL instead of the gates logic for the eight rom, just to minimize the parts?


I know that the objective was to actually do it oldschool and actually use gated logic.


Do you have the schematics available, so I can easier understand the logic behind it?

I also checking the verilog file right now. maybe that is something to understand the logic from as well ...
Proud owner of 2 Schneider CPC 464, 1 Schneider CPC 6128, GT65 and lots of books
Still learning all the details on how things work.

SerErris

Okay, I did build it ... no waiting for my MotherX4 to arrive ...


I can build to more, if anyone is interested in one?






I am in Germany, so postage will apply.
Proud owner of 2 Schneider CPC 464, 1 Schneider CPC 6128, GT65 and lots of books
Still learning all the details on how things work.

revaldinho


Quote from: SerErris on 15:06, 19 February 22Would it be possible to setup a GAL instead of the gates logic for the eight rom, just to minimize the parts?

I know that the objective was to actually do it oldschool and actually use gated logic.

Do you have the schematics available, so I can easier understand the logic behind it?

I also checking the verilog file right now. maybe that is something to understand the logic from as well ...


Yes, the eightRom is aimed squarely for people who want the all old-school feel and/or the easy soldering and availability of standard 74 series components without any need for logic programmers and synthesis toolchains.


You could definitely suck most or maybe all of the logic into a GAL.  All the source files for the project are available in GitHub. The original schematic is actually a netlist because I use my own pre-processor to prepare the Eagle board scripts. The netlist (PCB source) is this one: cpc_eightrom.v


You can also look at the very similar logic for the sixROM board which uses a CPLD for the logic implementation. The functional Verilog (CPLD source) is this one: cpld_sixrom.v 

There's a lot of overlap in functionality between the two boards, but sixRom allows the lower ROM replacement too. I couldn't fit the additional logic for that in through-hole 74 series gates into the limited size of the EightROM board (freeware Eagle limit 80x100mm), but you probably would manage it if using GAL(s) instead.



Bryce

#136
Quote from: SerErris on 16:54, 19 February 22
Okay, I did build it ... no waiting for my MotherX4 to arrive ...


I can build to more, if anyone is interested in one?






I am in Germany, so postage will apply.

That's extremely good soldering!

Bryce.

Edit: And good old leaded solder, none of this modern lead-free rubbish!

SerErris

Thanks...


Developed my skill over the years :-)
Proud owner of 2 Schneider CPC 464, 1 Schneider CPC 6128, GT65 and lots of books
Still learning all the details on how things work.

SerErris

@revaldinho I want to build a 512k RAM card for my CPC464. Can I use the XC9572 instead of the XC9536? I do see some code parts in the github repository, but as the screenshots all show the XC9536 I just wanted to make sure, that it does not break anything if I use the larger one?
Proud owner of 2 Schneider CPC 464, 1 Schneider CPC 6128, GT65 and lots of books
Still learning all the details on how things work.

revaldinho

Quote from: SerErris on 11:39, 03 April 22@revaldinho I want to build a 512k RAM card for my CPC464. Can I use the XC9572 instead of the XC9536? I do see some code parts in the github repository, but as the screenshots all show the XC9536 I just wanted to make sure, that it does not break anything if I use the larger one?

Yes. XC9572PC44 and XC9536PC44 are totally pin compatible and there is an XC9572 JED file in the releases area already for you. However, do not use the XL types - these are not the same thing at all.

XC9572PC44s are getting harder (and more expensive) to find these days, but XC9536PC44s are still relatively cheap even if you have to get new-old-stock.

I have wondered about doing some alternate ATF15xx CPLD versions of cards.

revaldinho

BTW if you have an XC9572PC44 and haven't got the pcbs yet, you might want to build the 1Mb card instead. This is compatible with FutureOS and SymbOS 3.1.

SerErris

Thanx, I do have the boards already, now just waiting for the SRAM and the CPLDs. I will be alle top do 5 or so, in anyone wants one...
Proud owner of 2 Schneider CPC 464, 1 Schneider CPC 6128, GT65 and lots of books
Still learning all the details on how things work.

Fran123

Quote from: SerErris on 16:54, 19 February 22Okay, I did build it ... no waiting for my MotherX4 to arrive ...


I can build to more, if anyone is interested in one?






I am in Germany, so postage will apply.
What price?

Rabs55

Firstly, I think the old school 512k ram expansion project is excellent. It has been 30+ years since I made anything like this and I love it. Now I think I am nearly there with, all the soldering completed but I would like to continuity check all my connections.

Is there a pdf of the schematic I can follow?


FD

I have tried to get hold of the 464 universal expansion but I can't find one anywhere...

revaldinho

Quote from: Rabs55 on 10:18, 20 May 22Firstly, I think the old school 512k ram expansion project is excellent. It has been 30+ years since I made anything like this and I love it. Now I think I am nearly there with, all the soldering completed but I would like to continuity check all my connections.

Is there a pdf of the schematic I can follow?


Thanks for your comments and your interest in my open source projects.

I do get this question a lot, but there are no traditional schematics for any of my PCBs. I come from an ASIC/FPGA background and prefer to work with text netlists, so I made my own netlist -> Eagle PCB script tool. The actual 'schematic' for the old school board is in this netlist file .

revaldinho

Quote from: FD on 10:01, 23 May 22I have tried to get hold of the 464 universal expansion but I can't find one anywhere...
If you want to get hold of any of my projects it's always worth PMing me via the Wiki. I don't sell on eBay or anywhere else, but always happy to make up small numbers of boards for CPCWiki users. I usually build an extra one or two when making up boards to order, so I may even have one in stock. If not, I'm pretty sure I do at least have some spare PCBs and a few XC9536s to make up a small number of the 512K Universal boards at the moment - I'll check later.

Just one note - I am in the UK, and will only deliver via a tracked/insured postal service. In the EU the receiver may (probably) need to pay any incoming customs duty on top of that. This can make postage disappointingly expensive for European users, and you may prefer to source boards in the EU in that case. 

Rabs55

Quote from: revaldinho on 11:02, 23 May 22
Quote from: Rabs55 on 10:18, 20 May 22Is there a pdf of the schematic I can follow?

Thanks for your comments and your interest in my open source projects.

I do get this question a lot, but there are no traditional schematics for any of my PCBs. I come from an ASIC/FPGA background and prefer to work with text netlists, so I made my own netlist -> Eagle PCB script tool. The actual 'schematic' for the old school board is in this netlist file .

Great, thanks for getting back to me. I will look at the netlist. Sounds like another learning experience  :).

FD

Quote from: revaldinho on 11:13, 23 May 22
Quote from: FD on 10:01, 23 May 22I have tried to get hold of the 464 universal expansion but I can't find one anywhere...
If you want to get hold of any of my projects it's always worth PMing me via the Wiki. I don't sell on eBay or anywhere else, but always happy to make up small numbers of boards for CPCWiki users. I usually build an extra one or two when making up boards to order, so I may even have one in stock. If not, I'm pretty sure I do at least have some spare PCBs and a few XC9536s to make up a small number of the 512K Universal boards at the moment - I'll check later.

Just one note - I am in the UK, and will only deliver via a tracked/insured postal service. In the EU the receiver may (probably) need to pay any incoming customs duty on top of that. This can make postage disappointingly expensive for European users, and you may prefer to source boards in the EU in that case.


Thank you so much. I will PM you.

aerobaticant

Hi @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.

As you can see from the pictures it is detected OK.

Any suggestions of some good (6128?) games to try? ;)


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