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RE: [N8VEM-S100:988] 512MB DRAM / S-100 Card

Mike thinking some more, before we go for this route are you sure there is not a way to refresh one modern day PC style Gigabyte DDRAM type SIMM with a crude binary counter slamming wait states back to the CPU in the process.  The clock speeds we would be using are way lower that what these DRAMS are expecting.  It seem such a shame to have to be using 4X132 pin chips and 8 DRAM SIMMS with what is available today.  


John Monahan Ph.D
e-mail: mon...@vitasoft.org
Text:    mon...@txt.att.net

-----Original Message-----
From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of mike
Sent: Tuesday, July 17, 2012 6:05 AM
To: n8vem...@googlegroups.com
Subject: [N8VEM-S100:988] 512MB DRAM / S-100 Card

Hash: SHA1

So to arrive at a 512MB DRAM S-100 card with over-the-top memory bus, using the parts we've been discussing, you end up with 8 x 72-pin SIMMs and 4 x 132-pin PQFP packages, a hand full of bus-glue chips, a few dozen caps, and power supply.

The SIMM array would take up about half of the area of an S-100 card, accounting for some wiggle room to run tracks around.

I think the way to go would be to split the SIMMS into two groups of 4 (bank A and B), and I would see lining up the two banks horizontally side-by-side and pushing those down toward the bottom of the card since there won't be much going on down there except for the power supply coming in. So you have the bottom of the card pretty much fully occupied by the SIMMs.

That would leave the top half of the card free and clear where you should be able to fit the four 132 pin PQFP packages comfortably either on the back or front and still have space left for bus logic, which should be pretty minimal, a hand full of buffers I'm thinking.

If we went surface mount on the bus logic, we could mount those on opposite sides from the memory controllers if space constraints require it.

The long and short is that I believe it can all fit comfortably on one
S-100 board with a little bit of creativity.

- --Mike

On 07/17/2012 03:21 AM, mike wrote:
> So a 512MB DRAM card built around this chip would look like this;
> 4 V96BMC chips, 8 sticks of 64MB 72-pin SIMMs (I think the 72 pin 
> simms are looking like the most likely to be compatible with this 
> arrangement).

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