Date: Tue, 20 Aug 1996 17:56:48 -0700 From: "Michael L. VanLoon -- HeadCandy.com" <michaelv@HeadCandy.com> To: "Rodney W. Grimes" <rgrimes@gndrsh.aac.dev.com> Cc: jas@flyingfox.com (Jim Shankland), freebsd-hardware@freebsd.org Subject: Re: SCSI again: Asus SC200 vs. Adaptec 2940 Message-ID: <199608210056.RAA10672@MindBender.HeadCandy.com> In-Reply-To: Your message of Tue, 20 Aug 96 16:03:31 -0700. <199608202303.QAA08500@GndRsh.aac.dev.com>
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>> A follow-up question, that I hope is of general interest: how does
>> the SC200 stack up against the Adaptec 2940U? The SC200 is quite a
>The line between when to switch from a 53C810 (I prefer to refer to
>it by that number, as there are others besides the SC-200) to an
>AHA2940U is real wide, and kinda grey, but here are some of the
>things I use in helping clients decide this issue.
[Some suggestions deleted...]
I have been doing some testing over the last week or so between a
BusLogic BT956c (PCI Wide, but not Ultra) and an Adaptec 2940UW.
Unfortunately, I did not have an NCR 53c810 controller to mix in.
The tests were conducted on a P5/120 (Asus P55TP4N, 512K PB cache,
32MB EDO RAM), with the controllers mentioned above, a 2GB Seagate
Barracuda (ST32550N) approximately 45% full, and a 1GB Seagate Hawk
(ST31200N) completely empty. Both drives support tagged-command-
queuing. I tried to do at least half the tests against both drives
simultaneously.
I have concluded that these two SCSI controllers are almost completely
equal in performance, if you don't have tagged-command-queuing.
However, if you enable tagged-command-queuing in the Adaptec driver,
the performance increase is *very* substantial, at least in my tests.
Since the BusLogic doesn't currently have tagged-command-queuing in
the bt driver, it loses this particular point. (But remember, your
drives have to support it correctly, as well -- there are some older
SCSI drives out there that don't support, or have buggy support.
Hopefully all current drives on the market have decent support for
it.)
I don't know if the NCR has tagged-command-queuing support or not. If
it did, I don't think I would trust it (the NCR driver is OK for
workstation type stuff, as Justin pointed out, but it is known to be
buggier than either the BusLogic or Adaptec drivers).
>I do have to say that I have an order of magnitude more trust in the
>aha2940 driver, and on my ability to get a bug fixed when I need it
>(Hi Justin! Thanks for the _GREAT_ support!!) by sending the broken
>hardware to Justin and giving him some time to work on it.
On the other hand, the NCR is substantially cheaper than either of
these two cards. And, it's reliability is decent enough to run a
personal workstation. I don't think I'd run an important server on
one, though.
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Michael L. VanLoon michaelv@HeadCandy.com
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