Re: Fw: UDMA on 815e chipset

[Mike Dresser <mdresser@windsormachine.com>]

> Even though I see the error message, I think that UDMA 4 / ATA 66 must actually have been set, because hdparm now reports cache reads at 143.82 MB/sec and disk reads at 15.76 MB/Ssec. hdparm also reports that the HDD is in UDMA mode 4.

This seems low, I have a pair of IBM DJNA-352030 20 gig's in a machine at home, that cache reads at 86.49(celeron 300@450, probably a slower machine than yours, would account for the lower numbers), disk reads score at 14.78, in Ultra/33 mode.(my mb
doesn't support ultra/66).
 It's been so long since i bought the hard drives, that i can't remember if they're 5400 rpm or 7200.  Either way, it's doing better than that controller is running your 7200 rpm 30'er.

> Much the same thing happens if I try for ATA 100 / UDMA 5 by substituting -X69.  hdparm now reports that the drive is in UDMA mode 5, but I do not see any improvement in transfer speeds, from which I assume that my kernel cannot go higher than ATA 66.

Don't forget that no IDE drive out there, at this time, can saturate even Ultra/66.  Unless you've got the newest and greatest, even Ultra/33 is wide enough for a single drive, unless you take into account the fact the cache can dump that whole
512k/2048k/whathaveyou at double the speed.
Granted, once you get two drives on the channel, Ultra/66 and 100 start making a difference, if they can share the channel efficiently.

Mike


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