Re: [math-fun] Miss those IBM/DEC blinking lights?
My first computer job (in high school) was working at the University of Cincinnati Medical School computer center, where we had an IBM 7040/1401 *tape* system (no disk!). The bulk of our computing work involved very long statistical regressions (some took all weekend) and radiation treatment planning (basically the inverse problem to a CAT scan). (Google University of Cincinnati Medical School and its dubious ethical history -- especially with DoD and radiation studies.) We also trained *blind programmers* (Google Dr. Theodore Sterling), who worked with the SW we developed for printing Braille on an IBM 1403 printer modified with a soft cloth behind the paper so that the paper would bulge after being hit with a ".". One of the blind programmers got so good at "reading" these 14" wide Braille printouts that he took his shirt off and simply pressed the printout against the skin on his chest! After our IBM "customer engineer" told us that computers interfered with radio reception -- and demonstrated this with a portable transistor radio -- the blind programmers started using this radio "side-channel" to let them know how their program was progressing. For them, it was the equivalent of our "blinking lights". (We didn't attempt to compute large powers modulo large primes, but these computers would have been so slow that one could have written down the bits of the exponents by hand from the radio signals.) At 09:25 PM 4/8/2018, Tomas Rokicki wrote:
I remember both the HP-21MX and PDP-11 lights as "glowing with varying brightness" but you could still figure out what your code was doing by just *how* bright individual bits were . . . I'm going to have to make a USB blinky-lights console for my Mac . . . maybe I'll put some toggle switches on it too.
An interesting and sometimes useful hack at the AI Lab circa 1970 was hooking an oscilloscope to the Program Counter. The high 9 bits drove X (I think) and the low 9 bits drove Y. The display thus showed from where in memory the instructions were being fetched, and brightness represented rate of executing that location. Loops looked like — loops! Unexpected behavior was sometimes clearly evident. 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. — Mike
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 --
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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I'm surprised that no one used the CRT+light pen to take pictures of the computer operator in the 1950's. (See the previous thread about one-pixel cameras.) The computer could display time-varying "stuff" on the screen and record the time-varying response from the single-pixel light sensor on the light pen simply sitting calmly on the desk. With enough time and enough resolution, one could conceivably take a picture of the (static) room, if not the operator him/herself. --- Human eyes can't distinguish flickering much above 60Hz, but LED's can reliably transmit bits into the MBits/sec range (remember those IR ports on older PC's?). The human operator may not be able to tell what the computer's doing from the console blinking lights, but another computer looking at the computer console through a window -- even from quite far away -- might be able to figure it out. At 12:46 PM 4/9/2018, 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.
I believe this is a well known method of spying on remote networks — look with high speed optical sensors through windows at the LEDs on network routers. Good routers will lowpass filter the LED signal.
On Apr 9, 2018, at 8:12 PM, Henry Baker <hbaker1@pipeline.com> wrote:
I'm surprised that no one used the CRT+light pen to take pictures of the computer operator in the 1950's. (See the previous thread about one-pixel cameras.)
The computer could display time-varying "stuff" on the screen and record the time-varying response from the single-pixel light sensor on the light pen simply sitting calmly on the desk. With enough time and enough resolution, one could conceivably take a picture of the (static) room, if not the operator him/herself.
--- Human eyes can't distinguish flickering much above 60Hz, but LED's can reliably transmit bits into the MBits/sec range (remember those IR ports on older PC's?). The human operator may not be able to tell what the computer's doing from the console blinking lights, but another computer looking at the computer console through a window -- even from quite far away -- might be able to figure it out.
At 12:46 PM 4/9/2018, 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.
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participants (5)
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Bernie Cosell -
Henry Baker -
Mike Beeler -
Tom Knight -
Tomas Rokicki