11/45 progress

[Jay West]

Tony wrote...
> Ah, but your memory is core, right? In which case, a 'read' is actually a
> write followed by a restore. Since you can read the same location and
> keep on getting the same data from it (you can do that, right?), the
> memory is basically working (for both read and write).
Correct, I'm aware core does the write after read. I'm suspecting unibus 
trouble but see below...

> You could try writing to something else (perhaps the data register on
> your conosle termial card) to see if you can write to anything on the
> Unibus. Or if you have a logic probe, you could see if the data lines
> pulse low when you try writing 1's to a memory location.
I'll have to figure out what address my console card is. I'll see if there's 
any docs on bitsavers for the M7800. If I'm reading some of the paperwork 
correctly, whatever memory address the card is set for corresponds to a real 
core location and I'd just read/write to that specific address (DEC has a 
rather odd definition of the word "register" to me) to see if the problem 
changes. However, if I have a unibus problem, isn't the M7800 which is in an 
SPC slot still going across the unibus? I haven't had my logic probe out in 
years... I thought it blipped on pulse high not pulse low. Surely that's 
settable. I'll check :) More germane info below...

One thing I noticed I'm not sure I mentioned. When I turn on both power 
supplies, 9 out of 10 times the system will come up with the pause and 
master lights lit. No switches on the front panel will do anything at all. 
Even setting the halt switch and hitting start (the lights change while 
start is depressed, but when releasing start the lights go back just the way 
they were and no switches change anything). The only way I found to turn on 
the system and have the front panel come up active is to move the halt 
switch to halt and then power up. Then I can read core, etc. I'm not sure 
what this behaviour means, but reading some docs I have it sounds like this 
indicates a problem with unibus getting to the memory.

Thanks for all the advice!

Jay West