Den 2016-07-25 kl. 14:37, skrev Camiel Vanderhoeven:
Op 25 jul. 2016 2:25 p.m. schreef "Göran Axelsson" <axels...@acc.umu.se>:
My guess so far is that there is a problem with reading and writing to
the memory. The problem is that I have no documentation over the memory
module except a drawing of the circuitry used to access it. ND bought
several different models of core memory for it's early computers and just
adapted the interface.
So once again I turn to the cctech for help, does anybody have
instructions about ExpandaCore 18 from by Cambridge Memories INC, Newton,
Massachusetts (also known as CMI but probably not the CMI on bitsavers).
So far the only thing I've found was a newsflash in a computer magazine
about a sale of memories to another computer maker.
I can't help you with that, but is it just the core stack itself you don't
have docs for, or does the CMI part include some driver circuitry? If it's
just the stack, you should be able to do without docs for that. Core memory
doesn't go bad unless it's physically damaged. If it is physically damaged,
repair can be very difficult, depending on the diameter of the cores.
Thanks for the answer.
The ExpandaCore 18 (tm) ;-) is a unit with the driver electronics and
core memory together. One control board per four memory planes and dual
ported so a high speed device could write straight into the core memory
without going through the CPU. In my case it seems like I have a packet
drive interface that uses the second channel.
I have put up some more pictures here :
http://www.home.neab.net/gandalf/ClassicComputing/Pictures/Nord-1%20%2347/
Maybe I'm jumping to conclusions here but there is one "control board"
for each four core planes. Maybe it's just a buffer. A problem with the
core memories is that it sits tight in a crate and I have no extender
for these cards. At least I should be able to measure the signals from
the CPU to the control board, and from the control board to the memory
planes.
How are you troubleshooting this? Can you deposit a value in memory from
the front panel, then read it back? If that works, but one or more bits are
off, there's a good reason to look at the core driver circuitry. If it
doesn't work at all, the problem could be anywhere. Try hooking a logic
analyzer to the address and data lines, clock, and read/write control lines
for a start.
Good luck!
Camiel
I can deposit a value in the address register (R) but that is as far as
I have come right now. I can also look at the other registers. I think
that the memory content should show up when I enter an address but I get
back the same value as I entered.
The operators panel is a bit broken down, there are a couple of bad
switches but new ones is in the mail. Some keys react on vibrations.
At the moment I can't do any measurements on the CPU-cards as there are
no space in that crowded rack. But yesterday I cadded an extender for
the NORD-1 CPU crate so in a week I'll be able to do some measurements
on that part at least.
I got a cheap USB-connected logic analyzer and a digital sampling
oscilloscope, so with the extender cards I will be able to measure or
break up and inject any signal I want in the CPU.
This is too fun to be healthy! :-)
Göran
