While I have the case open...

[Thaddeus P. Floryan]

In article <550 at trux.UUCP> car at trux.UUCP (Chris Rende) writes:
>I'll be opening the case of my 3b1 in the near future.
>[...]
>What markings or numbers should I look for that may be of future interest?
>[...]

The board "schematic" number (in copper) near the left rear corner is quite
useful when referencing one of the three sets of schematics in the Reference
Manual.  Often the copper number is obscured by a white sticker bearing a
different number.  BOTH sets of numbers "almost" uniquely identify your
machine.  Peel the white sticker off and reapply it flanking the copper number.

The copper board number will (usually) be one of 60-00222-00, 60-00225-00 or
60-00230-00.  If yours is 60-00216-00 you have my sympathy (the connector to
the floppy drive may be pin-for-pin reversed from that found on all other
motherboards, and you probably have the daughterboard above the motherboard).
The white paper sticker will bear a printed number something like "60-00237".

The OTHER "number" to write down for future reference is the "REV.n" value
on the white sticker normally found near the volume control sliding pot; this
will be something like "REV.C", "REV.F", "REV.J", etc.

The combination of the two sets of reference designators seems to uniquely
identify all 3B1 systems I've seen.  And note that a "REV.C" on a "225" board
is NOT the same as a "REV.C" on a "230" board.  And, before you ask, I have NOT
been able to determine precisely what each "REV.n" represents and I doubt that
information still exists even at CT (now UNISYS/NCG).

>I have a spare WD2010 HD controller chip that I got real cheap. Are there
>any advantages to installing the WD2010 if I don't plan to use more than
>1024 cylinders or more than 1 hard disk?
>[...]

If your system is one that DOESN'T have the "DRUN Patch" then putting the
WD2010 in your system will cause you a LOT of grief.  From my observations
on MANY systems, it's not always obvious whether the patch exists on one's
system; some factory runs implemented the patch along the lines of what I
described in my posting last December, and some runs had the patch integrated
into (presumably) new motherboard layouts where the legs of the 74123 chip
are NOT sticking up in the air.  If the resistor at R63 has the color code
bands, then the presence of 4.75K 1% means the patch is already applied (the
value of 6.81K 1% means you have the old data separator circuit which will NOT
function properly with a WD2010); if the resistor is the RN05 type (no color
bands) then you probably won't be able to read the value and you'll either
have to remove it (to read the value) or forget the whole thing.

The ABSENCE of a capacitor at C252 is also a good clue one's motherboard has
the DRUN patch already applied.

On other CT-built systems, the WD2010 was used from the factory and the CTIX
kernel ran the chip in ECC mode (usually) and a step rate value of 14 (vs. the
0 used in the 3B1/UNIXPC).  The difference is QUITE noticeable even to me (with
my bad hearing): a Maxtor will calibrate nearly instantly with a musical
"phweeeet" sound contrasted with the same disk calibrating with a "ehhhhhhh..."
sound on the 3B1.  I've observed a greater than 6:1 performance difference on
disk I/O (but that could also be due to the 68020, but ... ).   There was a
thread last year about altering the step rate with a WD2010 on the 3B1 but I
don't recall if any conclusive evidence appeared either way.

As long as your system will be open, you might want to consider replacing the
battery before the original one dies.  A circular battery holder and a 3V
lithium battery (about the size of a quarter) should cost no more than $2.50
total, and will make replacement during the year 2001 easier (the new battery
"should" last 10 years :-).

Thad Floryan [ thad at btr.com (OR) {decwrl, mips, fernwood}!btr!thad ]