[Coco] [Color Computer] 1M simms in Cloud9 SIMM upgrade kit

[Mike Pepe]

Paul, I'd love to see that, that sounds fascinating!

Paul T. Barton wrote:
> Mike,
> 
> Still, I think that it can be done.
> By using CAS before RAS DRAM internal refreshing.
> The DRAMs keep their own internal counter
> for this. Just swap RAS for CAS,
> only during HSync and/or VSync.
> I know that this works, I use it.
> 
> I could give out a partial schematic for this,
> if you want a look-see.
> 
> Paul
> 
> --- Mike Pepe <lamune at doki-doki.net> wrote:
> 
> 
>>Paul, Gene...
>>
>>I think you're right. I see a flaw in my theory
>>but practical testing 
>>seems to go with Paul on this one.
>>
>>A 256k DRAM, although it's "9 bits per axis"
>>actually only has 256 
>>columns (8 bit refresh)
>>
>>A 1M DRAM, whichi is "10 bits per axis"  only
>>has 512 columns (9 bit 
>>refresh)
>>
>>I would still think that in theory you just
>>don't use half of those 
>>columns and the memory works fine. I ran the
>>cloud9 memory test for 
>>hours and hours and hours and everything tested
>>fine.
>>
>>I then ran the practical peripherals memory
>>test just to verify  my 
>>results, and it reports errors with anything I
>>test except 256k modules. 
>>So, it's possible the algorithm in the first
>>memory test was keeping 
>>things refreshed but a more sophisticated test
>>shows some errors.
>>
>>It's too bad we can't hack that stupid GIME
>>chip. there's plenty of time 
>>to refresh a 1M chip as although there are
>>twice as many columns to 
>>refresh the time in which you have to refresh
>>it is doubled.
>>
>>Well it was an interesting experiment
>>nonetheless!
>>
>>Paul T. Barton wrote:
>>
>>>Mike,
>>>
>>>Just let it sit for a minute or so,
>>>doing nothing, it may crash. My experience.
>>>
>>>Paul T Barton
>>>
>>>
>>>--- Mike Pepe <lamune at doki-doki.net> wrote:
>>>
>>>
>>>
>>>>I was going to send this over to Mark at
>>
>>cloud
>>
>>>>9, but I figured I'd open it to the group.
>>>>
>>>>I'm unsing a Cloud 9 512k SIMM upgrade board.
>>>
>>>--snipped--
>>>
>>>
>>>>Then I got brave and installed a set of 1M 3
>>>>chip modules. They also 
>>>>work! I've been running a memory test on it
>>
>>for
>>
>>>>several hours and no problems reported.
>>>
>>>--snipped--
> 
> 
> 
> 
> 		
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