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%20System%20Pages/16M%20RAM%20Board/16MG%20RAM%20Board.htm#A_Third_Prototype_16MB_Static_RAM_Board
(Bottom of the page).
This board has the following
additional features:-
-
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.
-
I wanted to hand lay
down broad power traces to all the boards IC’s for
more even power distribution.
-
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.
-
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).
-
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.
-
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.
-
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.
-
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.
-
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).
John
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