Xerox D-series workstations

From: Kevin Schoedel <>
Date: Mon Nov 8 00:58:39 1999

At 7:19pm -0600 1999/11/07, Mitch Wright wrote:
> Somewhere you mentioned the company you work for made ucode compilers,
>assemblers. Anything left of these products laying around?

Depends what you mean by "laying around". We're still using the same
basic software (with improvements over the years, of course). Some
clients have rights to distribute them (in binary form) on their own
terms, so there may be some available somewhere, but I don't know.
Unfortunately I am stuck with enough NDAs that I'm not even sure which
past example I could name.

>Congrats on finding the Xerox machines, I've given up all hope of
>getting one.

Purely out of curiosity (and not because I intend to sell mine; I don't)
I checked ebay; someone sold a Daybreak for about $100 recently. Compared
to ebay prices of other things, this suggests they are not *too* rare. I
don't even want to *think* about how much I could sell the 8010 for
there, if I were to invoke the "S" word (even though mine has probably
always run Lisp, and is, by its memory and disk, clearly a late instance
as well). Don't tell me; I want to keep it :-)

A co-worker picked up the other of the two available Daybreaks; if he
gets tired of it, I'll let him know you might be interested.

On 1999/11/06 at 7:15pm +0000, Tony Duell wrote:
>But I've heard that the Daybreak uses the 80186 to load the control store
>at boot time. Whether it can load the control store once the machine has
>booted, or whether you have to rewrite the entire microcode and then
>reboot the machine (Ouch! I hope not), I don't know.

Part of the manual I've read mentions that the 80186 loads the control
store during booting "and debugging". I haven't yet seen how; I suspect
the details are not in any manual I have.

>Yes, I am on a dial-up connection, using an ancient 14k4 bps modem. And I
>generally start after 18:00, since that's when phonecalls become a little
>cheaper in the UK (is that the case elsewhere?)

In most of North America, a flat line charge includes unlimited local
calls; that's why people here throw around binaries with abandon.

>[....] I know I'm
>missing the keyboard and mouse (I picked it up cheap at a radio rally
>(hamfest), so I am not complaining). So I'll have to figure out the
>interface for those as well....

"The keyboard/interface uses the receive half of the i8251A interface
chip" suggests it's one-way communication. "... receive from the
keyboard as a differential signal pair by a 75176A receiver chip." I
don't know; does this imply RS232-compatible levels? "... asynchronous
serial interface with a data rate of 9600bps". I do not see the protocol
documented, but by the time you get around to your machine, I should be
able to hang my keyboard and mouse on some serial port and/or logic
analyzer to work it out.

>If fuse 1 blows even with A and B disconnected, then it's very likely
>that the transformer has shorted turns.

After removing the transformer, I believe I've confirmed shorted turns on
one half of the primary. Assuming no shorts in the secondaries, would
this not mean that the voltage I measured (15V) is an upper bound on the
correct voltage?

>If all else fails, dismantle the old transformer, unwind the wire, and
>count the turns.

I'm not sure I can do this accurately enough; the outermost layers seem
inextricably stuck in some hard resin-ish stuff.

>Still, all is not lost. There are
>ways to make some likely guesses as to what the transformer should be.

It appears to drive half of the front panel board -- the non-LED part.
Now, there's a 5V regulator (SG340K-5) there. The output is clearly Vcc
for the TTL on this half. The ground is clearly GND for the TTL and is
connected to one line from the secondary. The input of the regulator -- I
might be wrong again but I've double-checked -- is connected to the other
line of the secondary through a single diode (in other words, it seems to
be a half-wave); there's a 1000uF to ground.

So, one of the things I need to do is keep the regulator happy, which
seems straightforward; the question is whether the rest of the circuit
imposes tighter constraints. I can't easily trace it all because some
traces are hidden by the soldered-in TTL or the capacitor glued across
vital parts of the back of the board, so I'm trying to go by what I can
see and by considering why it's there. I can only think of two reasons
why this might need AC rather than just using the main power supply. It
might be a power-fail indicator, but I think that's implausible; since
the machine has semiconductor memory and power-hungry disks, there's
nothing it could *do* on power fail. And it does not seem consistent with
the parts on the board. But if this *were* the case, it would presumably
tightly constrain the required secondary voltage.

The other possibility I can think of is that it's a line-based
clock/timer. There are further diodes and resistors feeding (in a manner
I can't fully trace) a pulse generator (74123) whose output appears on
the cable from the front panel to the I/O board, and a trigger/inverter
(7414) which, I think, drives counters (74LS163) leading to a flip/flop
(74LS74) whose output likewise appears on the cable. Does this sound
plausible? And would it impose any tight constraints on the transformer

Kevin Schoedel
Received on Mon Nov 08 1999 - 00:58:39 GMT

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