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Date:      Sat, 18 Mar 1995 14:30:39 +1000
From:      Bruce Evans <bde@zeta.org.au>
To:        dleeds@eagle.ais.net, rgrimes@gndrsh.aac.dev.com
Cc:        hackers@FreeBSD.org, questions@FreeBSD.org
Subject:   Re: ultrastor 34f
Message-ID:  <199503180430.OAA07994@godzilla.zeta.org.au>

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>> I want to know if the ultrastor 34f controller (scsi-2) VL will work with 
>> freebsd, I heard it does, but want to know if it is stable and works
>> well before I buy it.

>The Ultrastor 34F does work, it is stable, it does have the nasty habit
>of causeing high interrupt latency as it seems to grab the bus for long
>periods of time.

``long'' is apparently about 250 usec.  For the BT445C the latency is
< 16 usec.  (I can't measure the overhead directly but I can measure
the maximum time that it takes for several instructions.  A U34F hogs
the bus in such a way that 10 inb() instructions take 250 usec longer,
while with a BT445C they only take 16 usec longer.)

There are some other problems:

1) media detection is not completely implemented in the driver.
2) there are some performance problems.  Command overhead is higher.
   The driver or the controller doesn't seem to handle scatter/gather
   well.  The speed of reading /dev/rsd0d drops by 40% when memory
   gets fragmented.

>Utrastor is also out of business, so if you are buying one get a real
>good deal on it.

>If any one wants one of these I will gladly sell mine for $150.00 as

$50 would be a good deal :-).

Bruce



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