The minimum you could get away with David would be 4 chips. The 80386 is a 32 bit CPU! Four chips would give you 8MG to get started on our 32MG board!
I don’t think it is worth a redo of the 32K SRAM board for a 2X increase because unfortunately we would have to redo the mezzanine boards as well.
However your observation is very relevant because Andrew and I are also doing a new “standard” 16M SRAM S-100 bus prototype board (the max capacity of the S-100 bus), we were going to use the Cypress CY62167DV30 2MX8 chips on two of the same above mezzanine boards, now I’m thinking why not pin 4 of these 4MX8 chips directly to the S100 board and be done with it. What do people think. Are most people comfortable these days with a little SMD soldering.
John
From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of David Fry
Sent: Wednesday, December 4, 2013 1:39 PM
To: n8vem...@googlegroups.com
Cc: mon...@vitasoft.org
Subject: Re: [N8VEM-S100:2100] 32 MB Static RAM Board for the S-100 80386 CPU Board
After my posting I noticed that Mouser have a large minimum order requirement but Digikey are showing 323 in stock with a minimum quantity of 1 unit.
they are the TSOP package and not the ball array package so do-able.
I agree on your point of going to DRAM for larger capacity but outside of my skill range I'm afraid, I just wondered if the AS6C3216 would permit a cost reduction for the 32Mb board as I am currently leaning towards the 8Mb board on grounds of cost.
Is it possible to partially populate the mezzanine memory cards with say 1 chip each to get started and maybe add the others later when prices reduce or does the design necessitate all 16 chips to be fitted ?
David Fry
On Wednesday, December 4, 2013 9:17:16 PM UTC, monahanz wrote:
David, the only ones I can find are TFGGA (ball) mounted chips. These require special ovens to attach to a circuit board. Not practical for most users. Have you see the normal SMD chips.
I’m really thinking after 32MG we need to somehow go to a DRAM board. The delta increase in capacity/price is no longer worth it for SRAM. Looking for a volunteer to lay out a DRAM controller etc.
Also FYI I am going to do a 80486 board next year.
John
From: n8ve...@googlegroups.com [mailto:n8ve...@googlegroups.com] On Behalf Of David Fry
Sent: Wednesday, December 4, 2013 11:32 AM
To: n8ve...@googlegroups.com
Subject: [N8VEM-S100:2098] 32 MB Static RAM Board for the S-100 80386 CPU Board
In anticipation of the likely new year release of the S-100 80386 board and associated memory boards I was pricing up the cost of memory chips for the 32Mb board and came across what appears to be a recently released chip from Alliance Semiconductor the AS6C3216 this chip (also surface mount) has double the memory density of the chips used on the 32Mb board mezzanine cards and seems to be priced at UK £9.98p at Mouser UK
Not sure if this is an option this late in the day to either double up to a 64MB board or lower the cost of building the 32Mb board, or maybe even allow an arrangement where the mezzanine cards can be added as funds allow for us more cash strapped builders :-)
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