Re: NEWSFLASH! Linux ported to Commodore VIC-20!!

H. Peter Anvin (hpa@transmeta.com)
20 Sep 1998 21:28:51 GMT

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

-- 
    PGP: 2047/2A960705 BA 03 D3 2C 14 A8 A8 BD  1E DF FE 69 EE 35 BD 74
    See http://www.zytor.com/~hpa/ for web page and full PGP public key
        I am Bahá'í -- ask me about it or see http://www.bahai.org/
   "To love another person is to see the face of God." -- Les Misérables


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/