On Thu, 20 Jul 2000, Vojtech Pavlik wrote:
> On Thu, Jul 20, 2000 at 04:25:28PM +0200, Rask Ingemann Lambertsen wrote:
>
> > A while ago, I asked on the T13 mailing list why you needed cable
> > detection in the first place when you have CRC checks, and thus know
> > exactly (at least after a few transfers) how good or bad the cable is. I
> > asked specifically if the CRC check used was too weak to allow you to
> > simply start out with the highest supported UDMA mode and then drop the
> > transfer rate if too many transfers failed the CRC check.
>
> Thanks a lot for the wonderful explanation. I've already read some of
> the T13 proposals, and wasn't sure what exactly they finalized on.
>
> Also, I have the feeling at least my BIOS only uses the CRC errors to
> switch to the appropriate UDMA mode - because it selects UDMA 16.6
> mode on a too-long 40-wire cable instead of UDMA 33.
>
> That'd probably explain why the VIA chipsets don't have any (documented)
> means of detecting the 80-wire cable presence.
Vojtech,
I tried to explain that to you. I am a voting member of T13.
Cheers,
Andre Hedrick
The Linux ATA/IDE guy
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