Vortex Expansions RAM card - how to upgrade

Started by eto, 20:22, 08 May 22

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eto

I got a 464 from Ebay where I unexpectedly found a Vortex Expansions RAM card - equipped with 64KB. Accoring to the documentation, it can be upgraded to 512KB by just replacing / adding RAM chips. However it's not specified exactly how. Neither on the Wiki nor in the manual. https://www.cpcwiki.eu/index.php/Vortex_Expansions_RAM_card

Does someone have more information about the card and how to upgrade it? Or can confirm my assumptions.

It uses 8xHM4864P-3 Ram chips and I would expect that I can replace them with 41256 chips, which I have laying around. On top of that, there is another empty bank, which I can populate. But there is also a missing IC, where I don't know which one that is and if that is required for the second RAM bank to work. It might be a CD74HCT373E like the one next to it. At least one of the pictures on the WIKI page has it populated too and has a mix of 4164 and 41256 chips.

Last but not least: In the manual there is one connection to the motherboard, however mine has a second connection that is not documented (black wire). Does somebody know for what this is required?

Picture attached.

TotO

The wire going to R112 is to control /ROMDIS
The wire going to R124 is to control /RAMDIS
"You make one mistake in your life and the internet will never let you live it down" (Keith Goodyer)

rpalmer

Quote from: eto on 20:22, 08 May 22I got a 464 from Ebay where I unexpectedly found a Vortex Expansions RAM card - equipped with 64MB. Accoring to the documentation, it can be upgraded to 512KB by just replacing / adding RAM chips. However it's not specified exactly how.
Wow, I did not know the card came with 64Megabytes and you wanted to degrade it to 512K.

eto

:doh: force of habit... KB/MB/GB/TB

aaaaand - corrected!

eto

Update: 4164 can be replaced by 41256 and the card autodetects the new size.
Still open, if adding a 74HCT373 will be sufficient to enable the second memory bank.

And I could not update the ROM to 2.1 - the 464 hangs during the boot then. Are there different ROM versions for 464 and 664 maybe? Just to be sure it's nothing with the burn process, I made a copy of the original ROM and that perfectly works.

SkulleateR

I have a working Vortex 512KB Ram expansion with BOS 2.1 rom, but I got no way to read out ... I can send it to you so you can make a dump If you want :)

eto

Quote from: SkulleateR on 02:43, 09 May 22I have a working Vortex 512KB Ram expansion with BOS 2.1 rom, but I got no way to read out ... I can send it to you so you can make a dump If you want :)
Is it built-in and working? Then we probably can dump the ROM more easily. 

SkulleateR

No, but it was working when I took it out some months ago ....

How to dump it then ? I can re-insert it next weekend :)

TotO

Quote from: eto on 01:12, 09 May 224164 can be replaced by 41256 and the card autodetects the new size.
It doesn't "autodetect", but just use the one more A8 multiplexed address line to go from 64 to 256. :)
"You make one mistake in your life and the internet will never let you live it down" (Keith Goodyer)

eto

Quote from: SkulleateR on 10:37, 09 May 22How to dump it then ? I can re-insert it next weekend :)
Very nice offer - but as it's quite some effort to do that and always also has the risk of damaging something, I'll try to find someone with a working expansion card who can dump the ROM - just a tiny tool is required. Not really worth the risk to damage something. 

I mean, it's obviously more for curiosity as there's not much use for this extension anyway as it's not compatible with DK'tronics. But I'd like to see it in full action and then enhance the WIKI entry with the information about RAM upgrade and of course with a proper ROM file (if it's really the ROM file that is not working). 

eto

Quote from: TotO on 11:44, 09 May 22It doesn't "autodetect", but just use the one more A8 multiplexed address line to go from 64 to 256. :)
forgive me my sloppiness: yes, the hardware does not autodetect - only the software does. What I basically meant is, that you just have to swap RAM chips and that's it. That's different from e.g. a DK'tronics upgrade, where additional components are required. 

eto

I looked into the BOS 2.1 ROM that is attached to the Wiki page and it seems not to be a valid ROM. Address of the name table is not correct and the jump block is somewhere in the middle of the ROM instead of the beginning.

So if someone is willing to dump the ROM, we could update the Wiki page with a valid ROM.

SkulleateR

Quote from: eto on 23:49, 10 May 22I looked into the BOS 2.1 ROM that is attached to the Wiki page and it seems not to be a valid ROM. Address of the name table is not correct and the jump block is somewhere in the middle of the ROM instead of the beginning.

So if someone is willing to dump the ROM, we could update the Wiki page with a valid ROM.
My offer is still valid ;) I just need to know how to dump it if I put it back into my 464 ... 

eto

Quote from: SkulleateR on 01:58, 11 May 22My offer is still valid ;) I just need to know how to dump it if I put it back into my 464 ...

OK ;-) I can provide you with a program that saves the ROM to a file.

SkulleateR


eto

dump.bas will dump the rom to disk. DSK attached or here the source:


5 MEMORY &3EFF
10 DATA E,7,CD,F,B9,78,32,26
20 DATA 3F,79,32,27,3F,21,0,C0
30 DATA 11,0,40,1,0,40,ED,B0
40 DATA 3A,27,3F,4F,CD,F,B9,3A
50 DATA 26,3F,CD,C,B9,C9,8D,0
60 FOR i=&3F00 TO &3F27:READ a$:POKE i,VAL("&"+a$):NEXT
70 POKE &3F01,6:REM ROM number
80 CALL &3F00
90 SAVE "dump.rom",b,&4000,&4000

I tried it with my BOS 1.0 and it perfectly worked. Fun fact: My BOS 1.0 is AGAIN a different version than the two BOS 1.0 that have already been uploaded to the Wiki.


eto

#16
UPDATE:

I got the information that Vortex liked to obfuscate their ROMs and that it might still work, although it looks like it's not working. A quick test with Winape (should have thought of that earlier) showed that indeed it will boot with BOS 2.1. So tried again with another Eprom chip, just in case it was the chip that was the problem. Still no success. But then I recognised that I have this additional wire from the SP512 to the mainboard, which is not mentioned in the manual =>  So I removed it. Et voilà - BOS 2.1 boots.

Success? NO! Now the card only recognises half of the RAM. Both ROM 1.0 and 2.1 only see half of the RAM. I have to connect the wire again to see the full RAM. Something must be different with this specific board as the wire is not mentioned in the manual. And since I can't find any reference about this card with this wire, I probably have to accept that it's only working with BOS 1.0

Edit: When looking at the other pictures on the net, my card looks much less finished. Lots of wires on the card, ALL ICs socketed... might this be a prototype?

@SkulleateR thanks for your offer. But unless your card also has that second wire going to the motherboard, I guess we can skip the ROM dump.

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