11 Nov
2006
11 Nov
'06
8:44 a.m.
Teo Zenios wrote:
This brings back a painful memory of reading a Jerry Pournelle column
while stuck on an airplane. I think he had such a system. It was an
80486 and he called it 'Cheetah'.
I'm actually kind of interested in learning how to do this. I have
several machines in varying states of disrepair, and the 512K memory
card is usually the common denominator. Instead of trying to repair the
card (a proprietary memory card in a Racore expansion unit for a PCjr),
I want to replace the card entirely with an implementation done using an
SRAM.
I know of somebody who did this, and I have his schematic. I can
certainly figure out the pinouts and mappings, but being a software
person and not a hardware person when it comes to board layout I get a
little fidgety. And my soldering skills aren't developed yet. (I won't
say suck until they are developed and do really suck.)
On the 512K card in question you get rid of 16 (no parity) 256K chips
and the DRAM controller. (It's a PCjr, so it uses a DRAM controller to
refresh add-on memory, not a DMA channel.) All that is left is address
decode logic and an SRAM. And you get rid of the refresh cycles too.
Mike
On 10 Nov 2006
at 13:55, woodelf wrote:
> Why not build a static ram card -- no dynamaic ram and really speed up
the
pc.
Back in the day, fast static RAM was fairly
expensive. Of course,
you could do this today, but where's the fun in that?
Cheers,
Chuck
Didn't some manufacturer sell a machine with SRAM instead of DRAM for a
short period of time when DRAM and SRAM prices were about the same? It was
supposed to be a screamer at the time.