WIP: internal 512K expansion

[McArti0]

Seriously, I doubt that this expansion will be a game changer.
Who needs more RAM already has an expansion.

I do not have and do not see on the market an obvious device called RAM for 6128 without a sauna, jacuzzi and helicopter landing pad.   
ps. I hate make PCB.

[McArti0]

Side question:
Are there any SRAMs with more than 512K that

• are 5V compatible
• easy to solder
• cheap

DS1265 nvsram EDIP-36 (A little bit tall)

[eto]

DS1265 nvsram EDIP-36 (A little bit tall)

and a little bit incompatible ;-)

[McArti0]

and a little bit incompatible ;-)

Why? https://www.analog.com/media/en/technical-documentation/data-sheets/DS1265AB-DS1265Y.pdf

I thought how much a working SRAM with a broken NV would cost.

btw: cheapest is piggyback 2x512kB and separate CE.

[GUNHED]

Then go got 4 MB all together. So it makes really sense: With 4 MB internal, no external additional RAM extension would be needed. 

[eto]

btw: cheapest is piggyback 2x512kB and separate CE.

piggyback won't work in the 6128. Simply not enough space between PCB and keyboard 

Why? https://www.analog.com/media/en/technical-documentation/data-sheets/DS1265AB-DS1265Y.pdf

ah okay, I only found the 3.3V version. But did you check availability and prices? A Ram expansion doesn't make sense if the parts are not available easily or expensive.

[eto]

Then go got 4 MB all together. So it makes really sense: With 4 MB internal, no external additional RAM extension would be needed. 

I probably can get up to 1MB at least for the 6128 version with 2 SRAMs. Anything beyond that requires different SRAMs.

Do you have a recommendation for the right SRAM IC? It should be

• cheap
• easy to solder (no TSOP package)
• 5V compatible

[McArti0]

Side question:
Are there any SRAMs with more than 512K that

• are 5V compatible
• easy to solder
• cheap

But I crossed out the "cheap" 

~30EURO/USD

[McArti0]

piggyback won't work in the 6128. Simply not enough space between PCB and keyboard

Maybe this way?

[eto]

Update: I could modify the prototype to test if a 1MB expansion is feasible for the 6128 and it probably can be done as the 2 GALs provide enough logic features for it. 

The final version will then be a single PCB which can be equipped with either 1 or 2 SRAMs and provide 512K or 1024K of expanded RAM.

[Prodatron]

Very cool, 1MB would be amazing!

[eto]

Update: The "beta" PCBs arrived last week - and of course I selected the wrong package size for the SRAM ICs. 

Anyway - at least I could confirm the PCB size and how much space I have. On the plus side I could confirm that I do have enough space for a full through-hole version even in the 6128. The same PCB size will also work for a 1MB version with 2 SMD SRAM ICs.

The (hopefully) final plan is now:

For the CPC 6128:

• iRAM/576 - all through hole, 512K expanded RAM
• iRAM/1088 - two SMD SRAM ICs, rest is through-hole, 1024K of expanded RAM (512K if only one SRAM IC is installed)

For the CPC 464/664:

• iRAM/512 - all through hole, 448K expanded RAM
• iRAM/1024 - two SMD SRAM ICs, rest is through-hole, 960K of expanded RAM (448K if only one SRAM IC is installed)

Notes:

• The 6128 version expects that the PAL is still present (C3 is handled by the PAL on the motherboard).
• The 6128 version probably also works in the 464/664 but without C3 support - and it won't fit with all motherboard versions of the 464.
• The 464/664 version will also work in the 6128 but doesn't fit into the closed case and wastes 64K of RAM.
• It will NOT work in the Plus models

The first revision of the iRAM/512 PCBs will hopefully show up next week. The second revision of the iRAM/576 will probably need another week at least as JLCPCB is not working Oct 1st-3rd and it's unclear when the PCBs will be made/shipped. 


I might need some beta testers that are willing to try it out in their CPC. Please think about it if you would like to help by doing an intense test of the expansion. Best would be if you have several use cases - and the willingness to install and test within 2 weeks after receiving the expansions. After the test you can keep the expansion of course. I'll make a separate post once I am ready to start the beta test, so no need to send messages already ;-)

[GUNHED]

Sorry to hear from the bad luck with the SRAM package size.   But go on with your great work, it's just amazing what can be done! 

[HAL6128]

Nice development. Do you have in mind what kind of test cases do you want to run?
. I couldn't support but only have some 6128 around.

[eto]

Do you have in mind what kind of test cases do you want to run?

My problem is that I am not really aware of which software takes advantage of expanded RAM over 128K. And for the few I found I'm not sure that I really can verify that it is working properly. E.g. I had the situation that it already worked and I thought it's fine as all RAM tests were successful. But then I recognized that some apps failed to run. SymbOS did not start as it failed during its internal RAM test - and Pinball Dreams failed. Everything else worked.

As I do not really have experience with expanded RAM software I would love to leverage the experience of anyone who is or was a heavy user of such software. E.g. I never used SymbOS before so any tests I do with SymbOS I would not see as reliable for all edge cases. So any SymbOS heavy user who knows how to use all the available RAM properly would be a great use case. Or RAM disk users. I couldn't find a RAM disk that uses all of the expanded RAM up to 1MB. And even if I would find one, I would not know how to fill it and then properly test it.

And except for those two use cases I actually don't even have an idea what other apps could exist that are using more than 128 or maybe 256K of RAM.

[Prodatron]

any tests I do with SymbOS I would not see as reliable for all edge cases. So any SymbOS heavy user who knows how to use all the available RAM properly would be a great use case.

When you run SymbOS and start at least one application you can be sure, that ALL modes are used with the exception of #C3.
#C1 is always used for accessing the form data by the Desktop Manager, #C2 always while an app is executed, and #C4-#C7 for accessing the ram >64K by the kernel. When you start as many programs as possible until the 576/1024K is completely filled, you know that it uses all 64K banks with all these modes (#C1,#C2,#C4-#C7).
So this would already be a very intensive test with nearly all "edge cases".

Or RAM disk users. I couldn't find a RAM disk that uses all of the expanded RAM up to 1MB. And even if I would find one, I would not know how to fill it and then properly test it.

I am pretty sure that any RAM disc implementation is only using #C4-#C7, but not #C1 and #C2, as these don't make sense for a RAM disc.

And except for those two use cases I actually don't even have an idea what other apps could exist that are using more than 128 or maybe 256K of RAM.

"Crime" (by Crown) is using more than 128K for copying discs.
I know my old CPC Word, which can use the full classic 576K for loading/editing text
But both are only using #C4-#C7 as well.

IIRC we had a thread here in the forum for listing all known programs, which are using more than 128K, but I would have to search for it first.

[eto]

When you run SymbOS and start at least one application you can be sure, that ALL modes are used with the exception of #C3.
#C1 is always used for accessing the form data by the Desktop Manager, #C2 always while an app is executed, and #C4-#C7 for accessing the ram >64K by the kernel. When you start as many programs as possible until the 576/1024K is completely filled, you know that it uses all 64K banks with all these modes (#C1,#C2,#C4-#C7).
So this would already be a very intensive test with nearly all "edge cases".

Seems SymbOS is the "best RAM test" available ;-)

Thanks for explaining the details. I'll try it.

[GUNHED]

When you run SymbOS and start at least one application you can be sure, that ALL modes are used with the exception of #C3.
#C1 is always used for accessing the form data by the Desktop Manager, #C2 always while an app is executed, and #C4-#C7 for accessing the ram >64K by the kernel. When you start as many programs as possible until the 576/1024K is completely filled, you know that it uses all 64K banks with all these modes (#C1,#C2,#C4-#C7).
So this would already be a very intensive test with nearly all "edge cases".

Seems SymbOS is the "best RAM test" available ;-)

Thanks for explaining the details. I'll try it.

And for true CPC6128-compatible RAM configuration you can use FutureOS. In case there are problems the mouse arrow will leave traces on the screen. 

[eto]

And for true CPC6128-compatible RAM configuration you can use FutureOS. In case there are problems the mouse arrow will leave traces on the screen. 

Already tested. C3 works. 

[GUNHED]

As usual you did a great job! 

[eto]

So the 464 version is here and I can properly run the RAM tests - but I'm not really sure if it really works as the only option I have on the 464 with the internal RAM is an M4 and I have no experience with it, so I don't know if the disk images I am using are the problem or the M4 - or if the RAM expansion doesn't work.


@GUNHED how can I start FutureOs from M4 on a 464? It is installed in ROM 10 and above but ROM 10 doesn't get initialised on the 464.

@Prodatron What's the best solution to run SymbOS from M4? I could mount a DSK but then I could not figure out how to start a program - I only get the error that no program can be found.

[d_kef]

M4 supports replacing the lower ROM as well.
So just install the 6128 ROMs and FutureOS will be initialized.

d_kef

[McArti0]

I could mount a DSK but then I could not figure out how to start a program - I only get the error that no program can be found.

Try rename sym. to sym.bas

Did you use a 180kB DATA disk?

[eto]

Did you use a 180kB DATA disk?

Sorry, I wasn't clear. I can start SymbOS 3.1. from the DSK image but when I am in SymbOS I can't start any other program there as I don't know how to access the application disk when I am in SymbOS. 

[McArti0]

Ah. did you use the second DATA Application disk?

And you can try found exe by menu Run...

Try my Big dsk too. I wonder if the M4 will chew it up.

ps. you cant change dsk?