A New 16MB Staric RAM S100 Bus Board

[monahan_z]

I would like to now introduce what will probably be the final version of our very reliable S100 16MB Static RAM board. It’s called the V5 16MB Static RAM S100 board. See here:-

http://s100computers.com/My System ...d.htm#A_Third_Prototype_16MB_Static_RAM_Board
(Bottom of the page).

This board has the following additional features:-

1. I did not want to change the basic RAM board circuit. It has proven itself time and again to be very reliable with any CPU board I could throw at it. Common easy to obtain 74LSxx chips are used throughout.
2. I wanted to hand lay down broad power traces to all the boards IC’s for more even power distribution.
3. I have inserted a trace “Keep out Area” on the front of the board so there is no danger of the 5V and 3.3V regulator heat sinks touching a critical trace beneath.
4. I added two 22V10 GALs to replace a number of 74LSxx chips. This greatly simplifies the board and somewhat speeds up the RAM access times. I realize not everybody is familiar with GAL’s. For those people who cannot program GALs and beginners ,I will supply the pre-programmed Lattice 22V10 GALs. The PALASM code is provided on the web page. These GAL’s are fairly common (Jameco #39159 for the 15ns variety).
5. I have added a wait state circuit (0 - 8 I/O wait states) to accommodate very fast S100 boards such as our 80386 and 80486 boards.
6. People should be able to simply switch IC’s from the old board to this new one. Two new GAL ICs is the only major change.
7. While the board is really built to meet the 16MB addressing range of the IEEE-696 bus, I have added jumper options so the board can be used in older systems like an Altair or IMSAI which only use a 16 bit address bus. Altair/IMASAI RAM write protect/unprotect can also be implemented on this board.
8. The board can accommodate EITHER the dual Mezzanine RAM boards described above (V6.0c), for 16MB of static RAM, or 8MB by soldering the 4 SMD CY62167DV30 static RAM chips directly on the board or 16M, by soldering 4 of the newer SMD AS6C3216 (4M X 8bit) static RAM chips on the board.
9. Last but least, I relabeled much of the Silk Screen to be more relevant. For example placing IC numbers above their pin locations etc.

Anyway I will do a group order for a batch of these V5 bare boards. Please let me know ASAP if you would like one or more bare boards. They will run somewhere between $14 - $16 each + shipping.
It’s best to send me an e-mail direct (monahan AT vitasoft DOT org).