Analyzer was Re: KIM-1 repair advice wanted

Brent Hilpert hilpert at
Sat Oct 8 03:14:35 CDT 2005

Scott Stevens wrote:
> Or you can use the "Poor Man's Logic Analyzer" which is a pair of D/A
> converters hooked to address/data lines and plugged into the appropriate
> address lines.  You hook the outputs of the DACs into an oscilloscope
> configured as an X/Y display and adjust gain so that it makes a grid on
> the screen.  It shows you dynamically where the software is branching in
> the memory map.  If you use this method regularly, it can be a
> 'signature analyzer' of sorts.  You'll get to know kind of dynamic
> display to expect and/or you can even write short diagnostic programs to
> 'draw' specific patterns on the display.

... Such displays originated back in the late-'40s/early-'50s with processors
using CRT-storage-tube memory systems. The digital-address-to-analog-deflection
circuits were already there for the storage-tubes, they simply had to be brought
out to a monitor tube. I recall reading the SWAC had such a display on one of the
two CRTs at the console. Whirlwind might/could have had as well.

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