On Sun, Jul 23, 2000 at 05:57:55PM +0200, Matthias Andree wrote:
> "Anthony Barbachan" <barbacha@Hinako.AMBusiness.com> writes:
>
> > I figured that with 40 wires missing the chipset or drive wouldn't allow
> > UDMA-66 anyway or that the drive would immediately stop working thus
> > preventing data curruption. If this is not the case and the drive can get
> > messed up then I would agree with defaulting to UDMA-33. Although I still
> > think the appropiate speed should be retrievable from the BIOS if not the
> > chipset itself. Another option is to allow the user to configure the
> > default from make menuconfig.
>
> Are those 80-ribbon cables by themselves marked/keyed in any way?
Yes.
> If so, the chip set would need support to read the key.
There doesn't seem to be such on VIA and AMD chipsets. Most other
chipsets have the support.
> If not so (which I assume), you cannot tell if you have the proper cable
> unless you transfer data and trash it.
>
> You might try to actively probe (like reading inquiry data at UDMA/16
> and UDMA/66 and compare it), but this may succeed, while subsequent
> transfers fail. You never know.
Fortunately all UDMA transfers are protected by safe enough CRC to see
if a transfer fails. This way you can know your cable won't do UDMA/66
and switch to something slower. (UDMA/44 seems to work on most 40-wire
cables just fine). If that doesn't work, go even lower. Something like
modem autobauding ...
> High-frequency technology requires care and thought. It's not about just
> switching DC on and off. There's more to it.
Yes.
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This archive was generated by hypermail 2b29 : Sun Jul 23 2000 - 21:00:20 EST