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From: kim@amdahl.amdahl.com (Kim DeVaughn)
Newsgroups: comp.sys.amiga
Subject: Re: The time (my watch has troubles) has come ...
Message-ID: <17264@amdahl.amdahl.com>
Date: Thu, 29-Oct-87 21:07:11 EST
Article-I.D.: amdahl.17264
Posted: Thu Oct 29 21:07:11 1987
Date-Received: Wed, 4-Nov-87 02:34:17 EST
References: <16531@amdahl.amdahl.com> <2541@cbmvax.UUCP>
Organization: Amdahl Corporation,  Sunnyvale, CA 94086
Lines: 36
Keywords: I should learn to RTFM
Summary: everything's a tradeoff (sigh)

In article <2541@cbmvax.UUCP>, andy@cbmvax.UUCP (Andy Finkel) writes:
> In article <16531@amdahl.amdahl.com> kim@amdahl.amdahl.com (I) wrote:
> 
> >Yep ... the jumper was between pins 2 and 3 rather than the pictured default
> >between pins 1 and 2!  So the timer chip had been getting popped at the
> >vertical sync rate, rather than being locked to the line frequency.  No big
> >deal, just swap the jumper.  Now the question is ... why would one want to
> >drive the timer from the vertical sync, rather than from the line?  Maybe
> >for use in areas with ill-controlled power?
> 
> This makes it compatible with the A500 which doesn't have the tick
> coming from the power supply :-(  but must rely on the vertical
> sync line for its timing, which we know is.........

Strange that it (the 500) doesn't pick off the line frequency ... doesn't
seem like much of a cost savings not to.

An "interesting" side effect of changing the jumper from the video sync to
the line tick, is that my floppy now *grinds* noticibly LOUDER (gak!)
Everything is nice and tight, mounting wise, so it must be due to the
slight difference in timer interrupt rates (resonance ?)  Sounds pretty
fishy, but I don't have a better explanation ...

Last night, I installed a 2nd 3.5" floppy, and *it* is REALLY quiet ...
literally, quiet as a whisper.  It's the exact same Matsushita drive
(model, assembly level, etc.) as df0: but *much* quieter than df0: was
even before I changed the timer jumper!  Oh well ...

/kim


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