I dunno what to make of it, other than
"UDMA is broken on the Promise Ultra33" card.
I have had one of these cards for over a year now,
but only ever used it for secondary drives.
I recently moved my primary filesystem over to
a drive on the Ultra33 card, and Boom!
Data corruption.
I have experimented extensively with it now,
verifying correct initialization of the chipset,
and playing with the PCI timing bits in the "System Control"
register -- no lucko.
The corruption seems to happen only when there is contention
between the Ultra33 and another PCI bus-master.
The card still seems to work flawlessly in PIO (PCI target) mode,
so that's exactly how I'll be using it from now own.
Much slower though!
I suppose it is no wonder that the card is buggy,
given that the PDC20246 chip is actually a re-labelled CMD646 chip
(pin 2 at power-on selects between CMD646 and PDC20246 modes).
Everybody remember the CMD640..? Same designers worked on this one.
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