Newsgroups: comp.sys.ibm.pc.hardware
Path: utzoo!utgpu!cunews!bnrgate!bigsur!bcars53!mussar
From: mussar@bcars53.uucp (G. Mussar)
Subject: Re: Computer slow since installation of SCSI drive
Message-ID: <1990Dec9.195558.16216@bigsur.uucp>
Sender: news@bigsur.uucp
Organization: Bell-Northern Research, Ottawa, Canada
References: <4076@mindlink.UUCP> <1990Dec9.050509.1470@vax5.cit.cornell.edu>
Distribution: comp
Date: Sun, 9 Dec 90 19:55:58 GMT

In article <1990Dec9.050509.1470@vax5.cit.cornell.edu> hd7x@vax5.cit.cornell.edu (Sanjay Aiyagari) writes:
>In article <4076@mindlink.UUCP>, a516@mindlink.UUCP (Jordan Melville) writes:
>> I recently got a new Quantum 210Meg SCSI drive, and notice that
>> since I got the drive, the video output has been substantially
>> slower (to a level where it is visibly noticeable, I can see screen
>> updates lag behind what they used to). Norton's SI still returns
>> the same values for processor speed, and the system gets the same
>> MIPS value. Could the SCSI drive have anything to do with this?
>> It's running on a Future Domain SCSI controller (model TMC-885),
>> inside of a 20Mhz 386 machine. I'm using ATI's VGAWonder card. The
>> drive is partitioned with the software provided with the drive with
>> two 105Meg separations. I am loading the dmdrvr.bin program that
>> came with it.
>
>This sounds strange, but one possibility (I'm not sure but it is possible) is
>that the new hard disk controller is causing a conflict in the C000/D000 areas
>of memory, causing the VGAWonder to use 8-bit ROM access, rather than 16.  If
>you are using video RAM shadowing, then this is not the problem; if you are
>not, then try using video RAM shadowing.  This will copy the ROM into RAM and
>will ensure it is being accessed 16 bits at a time.
>Sanjay Aiyagari (hd7x@vax5.cit.cornell.edu)

You can't shadow the video RAM only the video ROM. (What good would it do for
you to be reading/writing the shadow RAM when the video controller was still
displaying the card's RAM?). But, the 8/16 bit access to video RAM can be
a problem. If the system detects ANY 8 bit card in the same 128K address range
as the video card, all access to the video RAM will be 8 bit (we've measured
more than 2x decrease in performance).
--
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Gary Mussar  |Bitnet:  mussar@bnr.ca                  |  Phone: (613) 763-4937
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