Re: Two hdds on one channel - why so slow?

From: Krzysztof Oledzki (
Date: Wed Jan 02 2002 - 12:21:25 EST

On Tue, 1 Jan 2002, Brian wrote:

> This is an inherent quirk (SCSI folks would say brain damage) in IDE.
> Only one drive on an IDE chain may be accessed at once and only one
> request may go to that drive at a time. Therefore, the maximum you could
> hope for in that test is half speed on each. Throw in the overhead of
> continuously hopping between them and 12MB is no surprise.

So?!? This ATA100 and ATA133 standards do not make any sens? It is not
possible to have more than 66 MB/sec with on drive and is seems that it is
not possible to use more than ~30MB/sek of 100 or 133 MB/sec ATA100/133
bus speed with two HDDs. Oh :(((

Another question - why ATA100/ATA66 HDDs are so slow with UDMA33?
With new IBM 60 GB IC35L060AVER07-0 I have much more than 33 MB/sec with
ATA100 and only 24 MB/sec with UDMA33 (Asus P2B with IntelBX). New 80GB Seagates
(Baracuda IV) have the same problem.

Best regards,

                        Krzysztof Oledzki

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