On 1999/11/08 at 8:00pm +0000, Tony Duell wrote:
>I paid \pounds 10.00 for mine (machine + monitor + cartridge tape drive +
>floppy drive) at a radio rally (hamfest). No idea if it works or not, of
>course, but I was _very_ happy with that price.
I actually paid more for mine, because it looks too much like a modern
PC, and *less* for the 8010, because it's obviously too old to be good
for anything.
>[....]
>I wanted it to compare against the PERQs. From what I can see from
>glancing at the Daybreak there are similarities.
I still owe a summary of the microinstructions; unfortunately my 'main'
machine is a 'classic' in its own right (i.e. it's old) and one of its
disks, containing my notes, suddenly and catastrophically failed
yesterday.
Here is a very brief summary:
00 - 03 rA 2901 register number
04 - 07 rB 2901 register number
08 - 10 aS 2901 alu sources (A,Q; A,B; 0,Q; 0,B; 0A, D,A; D,Q; D,0)
11 - 13 aF 2901 alu op; the table in the manual is obviously botched
14 - 15 aD 2901 destination (values for rB, Q, Y bus)
16 - 19 Cin,enU,mem carry in; memory op (cycle dependent); U register op
20 - 23 fS determines interpretation of fY and fZ fields
24 - 27 fX misc operations (mostly seq call/ret, push/pop)
28 - 31 fY misc, encoded per fS, includes branch ops, or immediate
constant
32 - 35 fZ misc, encoded per fS, or immediate constant
36 - 47 INIA immediate next address
The next address is the INIA field optionally ORed with bits determined
by branch ops in the previous instruction.
Cycles are grouped in "clicks" of three cycles (c1, c2, c3) which
determine the interpretation of the 'mem' bit: address, read, write. Five
clicks form a "round". There are multiple (presumably six)
microinstruction pointers ("tasks"), corresponding to clicks in a round.
Each click in a round is associated permanently with and I/O service
routine; during any particular click, either that I/O routine executes
(if the device so requests) or else the macroinstruction interpreter
executes.
Besides the 2901 R registers, there is a 16 x 8-bit RH register set,
grouped with the corresponding R registers to form memory addresses.
There is also a 256-word external register set U, 16 words of which can
be quickly accessed by a stack pointer.
The large gate array on the CPU board is the sequencer/decoder; the
smaller one is the bus controller.
>Yes, I know the Daybreak is by far the most common D-machine, but that
>doesn't mean it's not worth saving. And it's the only D-machine I'm
>likely to find.
I didn't mean to suggest they wouldn't be worth saving. I'd never pass
over a non- commodity-microprocessor machine at any tolerable price.
(I've even bought uninteresting machines (cheaply) from that same source
just to make sure that they know that 'big, old' computers are *saleable*
and should not be scrapped. Anyone want three Sun 3/160's?)
>Incidentally, sorting out Xerox stuff is made harder because many of the
>ICs are house-coded with 733W... numbers. Sometimes you can guess the
>equivalents. But if anyone has a cross-reference list....
On mine, there are *very* few parts that have 733 numbers only. Nearly
all have only obviously generic numbers (e.g. 74LSxx), or both generic
and house numbers. The schematics appear to use only generic numbers.
>[....]
>OK, I've pulled the I/O processor from my machine and done a little
>looking (FWIW, this is not 'trivial' info, as it took me more than 10
>minutes to figure out :-))...
The documents contain some schematics, but in their current form (PDF
bitmaps) it's really difficult to find anything in particular. Once I'm
able to print them it should be possible to find things more easily.
>[....]
>The pinout of the keyboard connector (a DE-9) seems to be :
>
>1 A (One differential I/O signal from the 75176)
>2 B (the other one)
>3 Ground
>4 +5V
>5 Open collector output, driven by another bit of a '273??
Keyboard reset.
>6 +5V
>7 Ground
"unused"
>8 High-current-ish transistor output. Maybe to drive a speaker
Yes.
>9 Open collector output (from a '06). Input to this driver from TxD of
> the 8251?
Can't find it.
Noted on the schematic: 1 start bit, 8 data, 1 stop; 1 to 3 bytes of
keyboard/mouse data per event.
>>From what I remember, the keyboard connector links to a PCB in the stand
>of the monitor that has a DIN socket for the actual keyboard and also
>links to the speaker. Unfortunately, the monitor is not easy to get to at
>the moment, so I can't quickly check this, or look at pinouts, etc. One
>day...
This is probably somewhere in the document as well, but I don't see it.
>[....]
>You know, I'd almost be inclined to try a 9V or 12V transformer and see
>what happens...
I'll probably try that next. The machine ran for a few seconds on my
initial trial (before the first fuse blew), when there obviously was
already a problem, which suggests that the voltage is not too terribly
critical.
--
Kevin Schoedel
schoedel_at_kw.igs.net
Received on Mon Nov 08 1999 - 19:27:43 GMT