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

[Paul T. Barton]

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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