Messages in this thread | | | Date | Tue, 10 Oct 2000 10:51:47 +0200 | From | Vojtech Pavlik <> | Subject | Re: Incorrect UDMA timing on VIA vt82c596b |
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On Tue, Oct 10, 2000 at 01:10:06AM -0700, Andre Hedrick wrote:
> These are two different issues. > One is host side detection and the other is drive side > detection/acknowledgement. > > ide0=ata66 overrides the host-rules > > ivb-byte93 overrides the mixed drive side rules. > > The only think that is safe to do is allow users to randomly fake the > driver over the 80c ribbon issue, but if te drive fails to sense the > capacitance it must reject the attempt because of the iCRC and normal high > penality of resets/downgrades t oa stable signal clock.
Yes, but there is often the scenario where you have an UDMA66 capable drive and a say ZIP drive which makes the 80c cable undetectable by the drive. In that case a command line option would help, so that the kernel doesn't have to be recompiled for that.
I think it'd be good to think of 'ide0=ata66' as an option that disables all the 80-wire checks and consider that option dangerous, but still very useful.
If you could get the byte93 stuff correct, I'd agree with you that the 'ide0=ata66' should not mess with it, but it's impossible to get it correct due to devices like IOMEGA ZIP.
> Have you read the Quantum ammendments to the signal level thresholds?
Well, yes.
> The crosstalk can cause mis-clocks and data-corruption. I will bet you > that these were systems that if you pull that drive out and put it into a > standard system it will fail. Those are special case where an OEM has a > drive maker adjust the skew tables to allow dirty tricks.
I'll have to try that.
-- Vojtech Pavlik SuSE Labs - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/
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