11/45 progress

[Tony Duell]

> 
> 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 

Might be listed as DL11-A through DL11-E. 

> 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 

Yes, exactly. My idea was to see if you could write to anything on the 
Unibus. If you can't, then the problem is probably in the processor. If 
you can, then the problem is probably in the memory.


> years... I thought it blipped on pulse high not pulse low. Surely that's 
> settable. I'll check :) More germane info below...

It doesn't matter. The data line is normally high, when you write a 1, 
the processor brings it low, and then lets it go high again at the end of 
the cycle. If your probe detects the rising edge, it'll still show 
something changing (which is what you care about here).

-tony