Messages in this thread | | | From | (H. Peter Anvin) | Subject | Re: NEWSFLASH! Linux ported to Commodore VIC-20!! | Date | 20 Sep 1998 21:28:51 GMT |
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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.
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