More memory on 7300

[Charlie Root]

I think it is time to straighten this all out.  Many people have posted mes-
sages in the past that say that the .5MB 7300 has room for an additional .5MB
of RAM, bringing you up to 1MB.  NOT TRUE!

The .5MB 7300 motherboard uses 72 - 4164 (64Kx1bit) DRAM chips.  Since there
are ONLY 72 chip spots on the UNIX-PC motherboard (same for both the 3B1 and
the 7300), this is the MAX. of no waitstate, on board ram, barring any mother-
board upgrades (see attmail!looney!cmv (Craig Votava)'s repost to unix-pc.gen
<2634 at ihuxz.ATT.COM>).

The 1MB motherboard uses 36 - 41256 (256Kx1bit) DRAM chips.  I do not know if
it uses the 3B1 style motherboard, or if it uses the 7300 motherboard with
a few jumper changes.  (These jumper changes are explained in the afore-
mentioned news article.)  Regardless, owners of this machine can install
another 36 DRAM chips, and have 2MB of no waitstate, onboard ram.

Lastly, the 2MB 3B1 motherboard has 72 - 41256 (256Kx1bit) DRAM chips.  This
motherboard does not have any jumpers to allow for greater/lessor amounts of
memmory.  2MB is the maximum amount of ram a UNIX-PC can have ON BOARD.

After this, up to 2MB of add-on memory cards can be places in the expansion
ports on the machine's back-side.  This way, you can reach the machine's
4MB memory limit.

Hope that clears up all the mud...

Jonathan Sadler
Computing Systems Lab (CSL)
Universtiy of Wisconsin - Madison