[Coco] Static RAM in CoCo3?

[Roger Merchberger]

Rumor has it that jdaggett at gate.net may have mentioned these words:
>Roger
>
>An HCT373A and some glue logic to use the the RAS and maybe the CAS lines to
>generate an Adress Strobe signal to aid in demultiplexing the address from 
>the Z-
>Bus.

Doesn't sound that difficult if one knows what one's doing, which with 
DRAM, I don't. ;-)

>You have to configure the SRAM in 256Kx16 for a 512K block. That would 
>require 4
>128Kx8 SRAMs.

Or one 256kx16. I've already found 'em for under $5.00. Alliance Semi's 
number for 'em is AS7C4098, and the datasheet is here:

http://www.ortodoxism.ro/datasheets/AllianceSemiconductor/mXvsvsu.pdf

The chip on the ReMem is 1024Kx16, IIRC. Replicate the hardware mods for 
the Disto 2M upgrade, and one could have a 2M CoCo in just a few chips. [[ 
Or, at least that's what I was thinking... ]]

>  At least on the surface it really does not look to be all that difiicult
>a task to do.

If I knew what I was doing WRT the DRAM->SRAM differences, I'd give 'er a 
go... ;-)

>You don't need dual porrt ram. Besides 512K bytes of dual port ram would 
>be a very
>expensive endeavor.

Dunno... depending on other parts, it might be able to be done for around 
$100 with dual-port RAM, I found some cypress units for about $60 (sample 
quantity) - however, they were BGA units... :-/

That was a very quick search, however...

>As for drams they are really not analog.  Drams use a method of charge 
>storage
>and trransfer. The refresh cycle is needed to maintain charge that is 
>stored in a
>memory cell.

The infinitely variable voltage on the capacitor on each DRAM cell is how I 
equate them to being analog devices... ;-)

>A 512K or even a 2M memory of SRAM on a COco would definitely be considerably
>lower power consumption off of the power supply. At rest SRAMs draw far less
>current than DRAMS.

The ReMem I quoted earlier has very nearly the same power draw (w/2Meg RAM 
& 4Meg Flash) as the original memory in the laptop (w/32K RAM & 32K ROM)

Honestly, tho - I'm worried less about power usage (assuming it doesn't go 
*way over* or anything) as I am about the ability to use newer, more easily 
available stuff to upgrade our CoCos.

Laterz,
Roger "Merch" Merchberger

--
Roger "Merch" Merchberger  --  SysAdmin, Iceberg Computers
  _±±_                          zmerch at 30below.com
(©||®)  If at first you don't succeed, nuclear warhead
  _)(_   disarmament should *not* be your first career choice.