PDP-11/10 repair started
henk.gooijen at hotmail.com
Sun Oct 4 15:26:44 CDT 2015
From: tony duell
Sent: Sunday, October 04, 2015 9:52 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: RE: PDP-11/10 repair started
> the microcode is "on the menu" for next weekend ...
> The system is a 11/10S, CPU is M7260 and M7261.
Are you sure that's an 'S'? I thought the 'S' was the M8260/M8261 board
set with the links to disable the bus arbiter so it can be used as a slave
Anyway, getting back to this... I had forgotten that the 11/10 loads the LED
data serially into a shift register on the console board. Is that clock and
running (on the console board)? Also check round the '150 mux on the data
board, that is the source of the bitstream for the LEDs
The switch logic seems to be sheet CONE in my printset (which is actually
the GT40, but it's the same processor). On the control logic board, ROM
E100 seems to determine the microcode address for console operations.
Start with CONE BUT SWITCHES L, which seems to be an overall enable for
It starts from the '154 E078 on that board (sheet CONE again). It is
the microcode ROM E105 (sheet CONG). Microcode program counter is E102
and E091 (sheet CONF). Also look at the CPU clock (sheet CONJ). Is it
not, look at those gates E013d, etc, that disable it.
That's something to be going one with anyway...
Yup, the clock and counter on the console board are running.
That's why the console maintenance tests 5 - 8 work, producing
the data patterns on the LEDs :-)
Thanks for the pointers! I haven't looked at the schematics yet.
Yes, it is an 11/10S.
AFAIK, the M7260 and M7261 is used in all 11/10 versions, and
of course all 11/05 versions. I could be wronge though ...
I guess you are confused with the M7265/M7266 (11/34) and
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