22 Sep
2014
22 Sep
'14
9:49 p.m.
On 9/6/2014 1:27 PM, Josh Dersch wrote:
On 9/6/2014 1:06 AM, Brent Hilpert wrote:
A brief update (and request for further information): I finally had
time tonight to sit down and dig into this (I've been busy and easily
distracted by new shiny objects as of late). Thanks to Brent's writeup
and DEC's documentation (both of which are well written and relatively
easy to understand) I'm pretty sure I've traced down the fault to a
diode on the core plane board (H214), contained within a DIP package
designated as a DEC 2501.
Of course, I don't have any of these going spare (and I'm not sure if
there are equivalents -- I have yet to find a datasheet). Anyone have
any information about these, have any (good) spares, or know where I
might find some replacements? I suppose I could just hack in a single
diode (assuming I can determine the specs) but that seems kind of ugly...
Thanks,
Josh
On 2014-Sep-06, at 12:53 AM, Brent Hilpert
wrote:
Thanks for all the info -- the core memory overview you put together
looks to be very helpful, and when I have some time (hopefully this
evening) I'll study it a bit more in-depth and see what diagnosis I
can apply to the 11.
Thanks,
Josh
On 2014-Sep-05, at 9:11 PM, Josh Dersch wrote:
Should have mentioned.. it could be a
64*64 matrix with
anti-coincidence addressing to further double it.
Basic testing (via the simple address test listed
here:
http://www.psych.usyd.edu.au/pdp-11/hints.html) reveals that most
of the 8KW of core (H215) and controller is working pretty well,
except for a 128 byte range between 012000(8) and 012200(8).
Within this range, all words read back as all zeros regardless of
what is written.
For 8K the most probable matrix size is 128 * 64 (binary pair
closest to the square root of the size).