LSI11 CPU Microm

[Mattis Lind]

lördag 24 mars 2018 skrev Douglas Taylor via cctalk <cctalk at classiccmp.org>:

> I was trying to put together a minimal PDP-11/03 using a quad width M7264
> CPU and got nothing, no ODT prompt.  I'm not sure the board is working.
>
> Searching the internet I came across this page which described a M7264 CPU
> board with a 'bad' MICROM
>
> http://www.datormuseum.se/computers/digital-equipment-corporation/qbus
>
> Quoting the page; "Using a logic analyser showed that the MICROM without
> label is not behaving well."


I guess I wrote that a couple of years ago. If I remember correctly the way
I did research into this was to attach a 40 pin DIP clip connected to my
logic snalyzer on on the various MICROM chips and there were no activity at
all when the board got out of RESET. Then I removed one chip at a time to
see if there were any difference. This particular chip made a difference.
After removing it there were busactivity.

I have not yet got around trying with -3.9V Bias chips to see if that make
the board run better.

If your board is the later E etch then it has 3.9V bias and you could
directly use chips from a KD11-HA board.


>
> Anyone know how a logic analyser would be used to determine this?  Other
> hints to debug this board?
>
> Doug


/Mattis