UNIX pc 2nd drive modifications (was Re: P5.1 upgrade instructions)

[Lenny Tropiano]

In article <792 at bagend.UUCP> jan at bagend.UUCP (Jan Isley) writes:
...
|>After much deliberation and the soon to be released 2nd disk drive upgrade
|>that will require this modification, I have decided to post the instructions.
...
Soon to be released?  The ICUS plans have been out for 6 months now.  I assume
you are talking about John Milton's soon-to-be-released board.  As far as
*REQUIRING* the P5.1 upgrade, I think you are misinformed (slightly).  The
ICUS plans for upgrading your 3B1 to accept two hard drives DOES NOT REQUIRE
the previous installation of the P5.1 upgrade.   I believe the same goes
for John's forthcoming board, although I could be mistaken.  The P5.1
FIELD upgrade's jumpers on the motherboard will speed up the installation
of the upgrades because some of the jumpers, as well as, the socket that
needs to be installed on the motherboard will already be there.   

Some of the wires will have to be disconnected and/or moved, but nevertheless
some of the previous P5.1 work won't be wasted.   The preprogrammed PAL
required for the P5.1 upgrade is *NOT* required for the ICUS 2nd drive
upgrade (only standard 74-series TTL chips, and a 26LS31 and 26LS32).

I believe John is using another type of PAL (obviously with different
PAL equations) for his upgrade, so the PAL will be a wasted part (and
probably the hardest part to get to do the P5.1 upgrade, since most
people don't have PAL programmers handy).

Both upgrades (ICUS and John's) will have the functionality that the
P5.1 FIELD upgrade gives, namely the additional head select line (for
hard drives >8 heads).

Hope this clarifies things a bit...
-Lenny

-- 
Lenny Tropiano             ICUS Software Systems         [w] +1 (516) 589-7930
lenny at icus.islp.ny.us      Telex; 154232428 ICUS         [h] +1 (516) 968-8576
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        ICUS Software Systems -- PO Box 1; Islip Terrace, NY  11752