Computer Old Farts Forum
 help / color / mirror / Atom feed
* [COFF] [TUHS] Monitoring by loudspeaker (was: BTL pranks)
       [not found] ` <202007120222.06C2MtdJ140032@tahoe.cs.Dartmouth.EDU>
@ 2020-07-12 11:58   ` 
  2020-07-12 13:25     ` crossd
  2020-07-12 14:58     ` fuz
  0 siblings, 2 replies; 4+ messages in thread
From:  @ 2020-07-12 11:58 UTC (permalink / raw)


[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain, Size: 811 bytes --]

(This should probably be on COFF because I don't think this has much
to do with UNIX.)


On 11 Jul 2020 22:22 -0400, from doug at cs.dartmouth.edu (Doug McIlroy):
> a loudspeaker hooked to the low-order bit of the accumulator played
> gentle white noise in the background. The noise would turn into a
> shriek when the computer got into a tight loop,

How did that work? I can see how tying the low-order bit of the
accumulator to a loudspeaker would generate white noise as the
computer is doing work; but I fail to see how doing so would even
somewhat reliably generate a shrieking sound when the computer is in a
tight loop. Please, enlighten me. :-)

-- 
Michael Kjörling • https://michael.kjorling.se • michael at kjorling.se
 “Remember when, on the Internet, nobody cared that you were a dog?”



^ permalink raw reply	[flat|nested] 4+ messages in thread

* [COFF] [TUHS] Monitoring by loudspeaker (was: BTL pranks)
  2020-07-12 11:58   ` [COFF] [TUHS] Monitoring by loudspeaker (was: BTL pranks) 
@ 2020-07-12 13:25     ` crossd
  2020-07-12 14:58     ` fuz
  1 sibling, 0 replies; 4+ messages in thread
From: crossd @ 2020-07-12 13:25 UTC (permalink / raw)


[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain, Size: 1077 bytes --]

On Sun, Jul 12, 2020 at 7:59 AM Michael Kjörling <michael at kjorling.se>
wrote:

> (This should probably be on COFF because I don't think this has much
> to do with UNIX.)
>
>
> On 11 Jul 2020 22:22 -0400, from doug at cs.dartmouth.edu (Doug McIlroy):
> > a loudspeaker hooked to the low-order bit of the accumulator played
> > gentle white noise in the background. The noise would turn into a
> > shriek when the computer got into a tight loop,
>
> How did that work? I can see how tying the low-order bit of the
> accumulator to a loudspeaker would generate white noise as the
> computer is doing work; but I fail to see how doing so would even
> somewhat reliably generate a shrieking sound when the computer is in a
> tight loop. Please, enlighten me. :-)
>

I would imagine a cap as a low-pass filter and a transistor as a poor-man's
analog comparator triggering a tape player on loop.

        - Dan C.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://minnie.tuhs.org/pipermail/coff/attachments/20200712/e43c2aa0/attachment.htm>


^ permalink raw reply	[flat|nested] 4+ messages in thread

* [COFF] [TUHS] Monitoring by loudspeaker (was: BTL pranks)
  2020-07-12 11:58   ` [COFF] [TUHS] Monitoring by loudspeaker (was: BTL pranks) 
  2020-07-12 13:25     ` crossd
@ 2020-07-12 14:58     ` fuz
  2020-08-23  8:58       ` [COFF] Monitoring by loudspeaker tih
  1 sibling, 1 reply; 4+ messages in thread
From: fuz @ 2020-07-12 14:58 UTC (permalink / raw)


[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain, Size: 1515 bytes --]

When the computer is in a tight endless loop, the accumulator takes the
same series of values every time it's in the loop.  Thus, instead of
white noise you get a sound whose frequency is the clock frequency of
the machine divided by the number of cycles spent by one loop iteration.

That's how you know that the machine is stuck in an endless loop: if it
was doing something useful, the values would change every iteration and
you would get white noise again.

Yours,
Robert C

On Sun, Jul 12, 2020 at 11:58:11AM +0000, Michael Kjörling wrote:
> (This should probably be on COFF because I don't think this has much
> to do with UNIX.)
> 
> 
> On 11 Jul 2020 22:22 -0400, from doug at cs.dartmouth.edu (Doug McIlroy):
> > a loudspeaker hooked to the low-order bit of the accumulator played
> > gentle white noise in the background. The noise would turn into a
> > shriek when the computer got into a tight loop,
> 
> How did that work? I can see how tying the low-order bit of the
> accumulator to a loudspeaker would generate white noise as the
> computer is doing work; but I fail to see how doing so would even
> somewhat reliably generate a shrieking sound when the computer is in a
> tight loop. Please, enlighten me. :-)
> 
> -- 
> Michael Kjörling • https://michael.kjorling.se • michael at kjorling.se
>  “Remember when, on the Internet, nobody cared that you were a dog?”
> 

-- 
()  ascii ribbon campaign - for an 8-bit clean world 
/\  - against html email  - against proprietary attachments


^ permalink raw reply	[flat|nested] 4+ messages in thread

* [COFF] Monitoring by loudspeaker
  2020-07-12 14:58     ` fuz
@ 2020-08-23  8:58       ` tih
  0 siblings, 0 replies; 4+ messages in thread
From: tih @ 2020-08-23  8:58 UTC (permalink / raw)


Robert Clausecker <fuz at fuz.su> writes:

> When the computer is in a tight endless loop, the accumulator takes the
> same series of values every time it's in the loop.  Thus, instead of
> white noise you get a sound whose frequency is the clock frequency of
> the machine divided by the number of cycles spent by one loop iteration.

A buddy and I did something somewhat related back in the early eighties,
when we were teaching ourselves programming, using, among other things,
his Tandy TRS-80 home computer.  We discovered that a cheap "transistor
radio", sitting close to the computer, would be affected by the noise
generated by it, and then we figured out that if we didn't tune it to a
radio station, we'd get only the noise.  Leaving that on as we worked on
a program, we got familiar with the sound of the code, and became able
to follow the execution by the changing patterns -- and if it did get
stuck in a loop somewhere, we'd not only hear it, but we would also have
a pretty good idea where it happened.

-tih
-- 
Most people who graduate with CS degrees don't understand the significance
of Lisp.  Lisp is the most important idea in computer science.  --Alan Kay


^ permalink raw reply	[flat|nested] 4+ messages in thread

end of thread, other threads:[~2020-08-23  8:58 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
     [not found] <20200711203020.GA1884@minnie.tuhs.org>
     [not found] ` <202007120222.06C2MtdJ140032@tahoe.cs.Dartmouth.EDU>
2020-07-12 11:58   ` [COFF] [TUHS] Monitoring by loudspeaker (was: BTL pranks) 
2020-07-12 13:25     ` crossd
2020-07-12 14:58     ` fuz
2020-08-23  8:58       ` [COFF] Monitoring by loudspeaker tih

Computer Old Farts Forum

This inbox may be cloned and mirrored by anyone:

	git clone --mirror http://inbox.vuxu.org/coff

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V1 coff coff/ http://inbox.vuxu.org/coff \
		coff@minnie.tuhs.org
	public-inbox-index coff

Example config snippet for mirrors.
Newsgroup available over NNTP:
	nntp://inbox.vuxu.org/vuxu.archive.coff


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git