> I've got a situation where a drive claims to be capable of supporting > UDMA/100, but it's in a noisy environment and gets lots of errors at > that speed. I'd like to limit it to UDMA/66 or even UDMA/33. That should never occur with a proper cable and I would be concerned the fault might be something more problematic such as speed misconfiguration or an incompatibility. Which driver is in use ? > The hdparm command should be able to do this but I can't run it until > the system has booted, by which time a bunch of CRC and possibly other > errors have already occurred. Ideally it should be possible to limit Only the data transfers are CRC protected and at high speed, but noise at low speed would be a real concern as the commands are sent low speed but without protection on PATA devices - so a bit flip can send a DMA to the wrong sector. > the speed starting as early as device detection, but I can't find any > way to do it. Is there support for such a thing or will I have to hack > it in? You can disallow DMA but not clip DMA to UDMA33 with the old driver. You could disallow DMA at boot and reallow it with a speed set by hdparm in your boot scripts... -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
