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SubjectRe: NEWSFLASH! Linux ported to Commodore VIC-20!!
Date
Followup to:  <19980920154436.61218@cerebro.laendle>
By author: Marc Lehmann <pcg@goof.com>
In newsgroup: linux.dev.kernel
>
> On Fri, Sep 18, 1998 at 05:35:00AM +0200, Kai Henningsen wrote:
> > pcg@goof.com (Marc Lehmann) wrote on 17.09.98 in <19980917122639.44336@cerebro.laendle>:
> >
> > The *PC speaker*?! We're not talking about a bloody soundblaster!
>
> I wasn't.
>
> > The PC speaker has a 1 bit input. Nothing like 5-6 bit. Also nothing FM.
>
> You should really read the code. It _is_ FM-modulated, and achieves this
> resolution (the carrier frequency is 18khz or higher). And no, it has one
> bit _output_, not one bit _input_ ;)
>

It's not FM, at all; the Linux PC speaker driver uses PDM (Pulse
Duration Modulation) with a high frequency clock to increase the
resolution; this works because Linux can toggle the speaker much
faster than the speaker itself can move, so you get a "smoothing"
effect here.

-hpa
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