8 Oct
2005
8 Oct
'05
1:14 a.m.
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.