From owner-freebsd-hardware  Mon Feb 21  1:45: 3 2000
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From: Soren Schmidt <sos@freebsd.dk>
Message-Id: <200002210944.KAA95712@freebsd.dk>
Subject: Re: separate udma66 controller possible, when only having udma33 bios
In-Reply-To: <20000220213711.A62313@titan.klemm.gtn.com> from Andreas Klemm at "Feb 20, 2000 09:37:12 pm"
To: andreas@klemm.gtn.com (Andreas Klemm)
Date: Mon, 21 Feb 2000 10:44:15 +0100 (CET)
Cc: freebsd-hardware@FreeBSD.ORG,
	ohoyer@fbwi.fh-wilhelmshaven.de (Olaf Hoyer), sos@FreeBSD.ORG
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It seems Andreas Klemm wrote:
> The Maxtor 54098U8 will be the only EIDE device in the machine.
> So would it be satisfactory, to run it with the on board EIDE
> controller ???  But you also told me, that the CPU utilization
> is less with UDMA/66. So ... if I want to save some CPU cycles,
> should I nevertheless use UDMA/66 ?!

There is no significant, ie mesurable difference when you only have
one device attached, ATA33 and ATA66 will do the job with no
user notisable difference.
There are also other reasons to stick with ATA33, _alot_ of the
disks claiming to do ATA66 actually dont. This is true for some
WDC, Quantum and Maxtors disks. The problem is that they simply
lockup when hit by lots of requests, fast back to back. The only
disk make that I havn't seen _any_ problems with are IBM...

> > Those Promise and Abit etc. Controllers come with their on BIOS.
> > Therefore, if you buy one of these (about 100 DM here in Germany (~U$50))
> > you are able to do UDMA/66.
> 
> Soren, what controller do you have ? I think it would be a good strategy
> to buy a controller, that you have yourself, since I have the feeling, that
> EIDE sometimes has something of "black magic" ...

I have a pletoria of Promise and HPT366 based controllers, all of them
work just dandy.

> Soren, could you please tell me, what ATA controller I should buy
> to have a smooth migration from SCSI to EIDE ? That would be very kind !

If you only have one disk, and the motherboard can do ATA33 use that.
If you need more than two disks, then buy an extra Promise or HPT366
based (ie Abit, SIIG) controller.
And if you want a disk that is garantied to work, buy an IBM preferably
from the new DPTA series, there are blindingly fast, and they work.

-Søren


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