28 Aug
2011
28 Aug
'11
10:46 a.m.
Does anyone have an Olivetti M24 or AT&T PC 6300 with the P8 version
display card close at hand?
The one I have has the display card very thorougly disabled (no I/O
or memory space accessible) by the setting of a couple of jumpers and
a jumper plug at position 5H on the display card. This is a 20-pin
DIP socket and looks suspiciously similar to the 14 pin jumper plugr
used to disable the P4 display card.
Can anyone tell me what's supposed to be at this position? Since
it's a 20 pin DIP, it could be a something simple such as an LS244,
or (groan) it could be a PAL. On the P4, it's an LS00, but that's
clearly not the case here.
I have schematics for the P2 board, but not the P8. If all else
fails, I'll take the board out and try to figure things out the hard
way, but I'd rather get the information the easy way.
--Chuck
28 Aug
28 Aug
11:23 a.m.
Can anyone tell me what's supposed to be at this
position? Since
it's a 20 pin DIP, it could be a something simple such as an LS244,
or (groan) it could be a PAL. On the P4, it's an LS00, but that's
clearly not the case here.
I don;t have the schematics, but my first guss, unfortunately, would be a
combinatorial PAL acting as a decoder for some of the address lines (and
manybe other signals).
-tony
2:24 p.m.
On 28 Aug 2011 at 19:23, Tony Duell wrote:
I don;t have the schematics, but my first guss,
unfortunately, would
be a combinatorial PAL acting as a decoder for some of the address
lines (and manybe other signals).
I hope you're wrong.
This is a strange 6300. The keyboard controller's been replaced with
a "piggyback" PCB with a TMS7000 microcontroller and an EPROM and
some glue. There's a small card that plugs into one of the secondary
(short green) slot connectors on the bus converter board that has
nothing but an 4Kbit 82S147 PROM on it. I don't know the reason for
either of those and can't find any documentation on them.
--Chuck
3:40 p.m.
On 28 Aug 2011 at 19:23, Tony Duell wrote:
I don;t have the schematics, but my first guss,
unfortunately, would
be a combinatorial PAL acting as a decoder for some of the address
lines (and manybe other signals).
Pulling the display cover plate off and doing a little circuit
tracing shows that this IC drives various selects and also CAS for
the display DRAM (4x4416).. In fact, it looks as if the HAL10L8 at
position 5G on the P2 revision of the display controller is exactly
the same part. So, without the real thing, it'd be a matter of
trying to synthesize a replacement. Not worth the effort for me.
I'll leave it to Dave.
--Chuck
29 Aug
29 Aug
10:41 a.m.
On 28 Aug 2011 at 19:23, Tony Duell wrote:
Do you ahve, or know anybody who has, this P2 versions? The 10L8 has
nofeedback terms, so the bare chip, remvoed from the PCb, must implelenmt
purely combinatorial functions. While I don't think HALs ever had the
fuse map verification circuitry (I've never mananged to find one you can
read out in a PAL programmer0, since it's purely combinatorial you could
try all 1024 combinations of the inputs, record the outputs and do some
kind of logic reduction on the result.
Shouldn't be too hard...
-tony
I don;t have the schematics, but my first guss,
unfortunately, would
be a combinatorial PAL acting as a decoder for some of the address
lines (and manybe other signals).
Pulling the display cover plate off and doing a little circuit
tracing shows that this IC drives various selects and also CAS for
the display DRAM (4x4416).. In fact, it looks as if the HAL10L8 at
position 5G on the P2 revision of the display controller is exactly
the same part. So, without the real thing, it'd be a matter of
trying to synthesize a replacement. Not worth the effort for me.
12:26 p.m.
On 29 Aug 2011 at 18:41, Tony Duell wrote:
Do you ahve, or know anybody who has, this P2
versions? The 10L8 has
nofeedback terms, so the bare chip, remvoed from the PCb, must
implelenmt purely combinatorial functions. While I don't think HALs
ever had the fuse map verification circuitry (I've never mananged to
find one you can read out in a PAL programmer0, since it's purely
combinatorial you could try all 1024 combinations of the inputs,
record the outputs and do some kind of logic reduction on the result.
I'll cast around a bit and see. 6300/M24 boxes are fairly uncommon
here, although I expect that they're pretty common in Europe under
the Olivetti brand. Judging from the P2 schematics, the 10L8 looks
to have the same programming across all (P2, P4, P8) adapters, so
that does widen the field a bit.
BTW, the 6300 I have runs fine with a VGA card installed. Doubtless
that (or an EGA) was the original reason for the modification.
--Chuck
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