eder@ssc-vax.UUCP (Dani Eder) (01/21/85)
> > We even knew if we had diagnostics in our compile by the sound of the > old 1132 printer....It had a different "rhythm.".....I remember talking > on the phone from home to a friend at the computer...in the background was > the printer ker-chunking out a listing for him.....I heard the > unmistakable tones of a diagnostic report, and told him he had better > fix his bugs and re-compile....He thought I was psychic! > Back in high school, we had an IBM 1620 that was just as old as I was. Someone had discovered that if you put an AM radio on the console near the typewriter, and tuned to the low end of the AM dial, you could hear all sorts of interesting noises. We never did figure out what caused them, but one guy wrote a program that would play songs, and after a while, you could tell what the computer was doing by the sounds it was making. It was lots of fun to be able to tell innocent bystanders "the printer will start in five seconds", and then have it happen. Dani Eder / Boeing / ssc-vax!eder / Ad Astra!(To the Stars!)
cottrell@nbs-vms.ARPA (01/30/85)
The way I understand it, everytime the cpu references memory it generates radio waves on ALL (lotsa) frequencies. The tones you hear are audio frequencies modulating the RF carrier. There are certain instruxions that in the degenerate case will copy from a register to a register repeatedly, in effect doing nothing, but as a side effect waiting a given amount of time before referencing memory again. Your program has two tables, one for the notes themselves (period not frequency), and one for the duration (depends on the period). The program picks up the first note & duration pair, loads a repeat count register with the period, does the funny loop duration times. Is this what you did, or am I way off base? By the way, I once wrote a program to make a high speed tape drive play a musical scale by writing successively shorter records one hundred times each. The records were 1000, 800, 600, 700, 500, 400, 300, & 200 16 bit words. Obviously this mechanical system is not as linear as the electrical memory reference one is! */