Messages in this thread | | | Date | Wed, 29 Jul 1998 09:17:39 -0500 (CDT) | From | "Andre M. Hedrick" <> | Subject | Re: 2.1.111: IDE DMA disabled...BLAH...BLAH... |
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On Tue, 28 Jul 1998, Mark Lord wrote:
> > As for the (U)DMA question, would it not be sensible for us to flag > > the drive capablities. > > No, it would not be. > > We cannot blindly (and dangerously) reprogram the DMA mode > of the drive without knowing what mode the IDE interface > chipset is trying to use. The two must match.
Agreed.
> If the chipset is BIOS-configured for UDMA, > then we could break things big-time by selecting DMA at the drive..
Agreed.
> The IDE driver already does the Most Sensible things by default, > leaving the chipset and drive settings as set-up by the BIOS.
However, consider the case of a BIOS-less chipset on an offboard card that must be programmed. The chipset is native to UDMA and is backwards compatable. In all cases the pci-config data must me set for any mode regardless of the drive's capablities. Without take this step, an UDMA would register in PIO 0 strength.
> If DMA fails, the IDE driver automatically falls back to PIO mode, > without loss of data or corruption of any sort.
This is a good thing, and it works with the case stated above. Since I am having trouble getting the method in question functional, it is nice that the breakout of a failed (U)DMA results in a clean transition back to PIO status.
I am not asking for high risk programming and data coruption, I have to much to lose. This single chipset may be a special case that does need to relearn what it can do each time it is booted.
Regards, Andre Hedrick
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