The fact that modern machines use address space randomization as a security measure would significantly affect our ability to "read" the lights; every run would display different PC-counter patterns, for instance. But if you used, for instance, source file index/line number rather than PC (which should be easily doable) you might end up with something pretty neat . . . On Mon, Apr 9, 2018 at 4:49 PM, Bernie Cosell <bernie@fantasyfarm.com> wrote:
On 9 Apr 2018 at 15:46, Mike Beeler wrote:
... Nowadays, even if the PC were easily available, instruction rate is way too fast for a CRT to keep up with, but perhaps a pseudo-random sampling would accomplish the same effect. However, it wasn’t helpful enough to be a great tool, IMHO.
Got me wondering. I worked with BBN's PDP-1d, which was a very tricked-out PDP-1 (it had two drums, 9-channel mag tape drives, the prototype of the PDP-6 memory bank machinery). All of that stuff had lights on almost every register. The 'lights bank' was the width of the PDP-1 console and went to the ceiling, packed with lights all the way (Mike might have see that system.. I don't think any of you had). I got very good at understanding what was going on in the timesharing system just by a glance at the lights. Mike got me wondering what that lights display would be like with modern components. The displays on the two drums would be unreadable -- all the lights on, but at varying brightnesses. Same with the main CPU registers and everything else. But then, beyond that, I got to wondering if a suitable savant could still do what I did but by understanding the brightness patterns as they flowed back and forth
/B\
Bernie Cosell bernie@fantasyfarm.com -- Too many people; too few sheep --
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