Path: utzoo!attcan!uunet!aplcen!uakari.primate.wisc.edu!sdd.hp.com!hplabs!hpcc01!hpbbn!hpgnd!hppcmart!martin
From: martin@hppcmart.HP.COM (Martin Croome)
Newsgroups: comp.unix.i386
Subject: Re: 80386 cache and VGA
Message-ID: <100003@hppcmart.HP.COM>
Date: 31 May 90 16:17:07 GMT
References: <8343@cognos.UUCP>
Organization: Hewlett-Packard, Grenoble PC Div., France
Lines: 41

>campbell@Thalatta.COM (Bill Campbell) writes:
>In article <8415@cognos.UUCP> dbullis@cognos.UUCP (Dave Bullis) writes:
>:>In article <8343@cognos.UUCP> dbullis@cognos.UUCP (Dave Bullis) writes:
>:>>I was told by one the local clone dealers that there are problems
>:>>with mixing 80386 25MHz cache systems and VGA cards.
>:>> ...
>:>
>:>I talked to the dealer again for more details:  He says that some 8-bit
>:>VGA cards caused the system to hang when booting.  16-bit cards are ok.
>:>
>I had exactly the opposite problem with a 33Mhz NIC Motherboard,
>32K cache.  It wouldn't writefloppy disks properly when using a
>16-bit Paradise board, but running with the board in an 8-bit
>slot or substituting an 8-bit board cured the problem.  This
>problem has also been reported on the HP-Vectra.  The article on
>the Vectra implied that the problem was with any O/S running in
>the 386 protected mode.
>

The problem is that with the Paradise card in 16bit mode the video RAM is
not fully decoded so the card will appear in each 1Mb block of the PC's memory
space.

The cache should not be enabled over the VGA card's RAM. If it was it would
cause problems with the card. Most PC's disable the cache on writes and reads
to and from memory at addresses between 0xA0000 and 0xDFFFF to avoid this
problem.

>-- 
>....microsoft--\                    Bill Campbell; Celestial Software
>...uw-entropy----!thebes!camco!bill 6641 East Mercer Way
>....fluke------/                    Mercer Island, Wa 98040
>....hplsla----/                     (206) 232-4164
>----------

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Martin CROOME                        !'s    - hplabs!hpgnd!hppcmart!martin
Hewlett Packard                      @'s    - martin@hppcmart.grenoble.hp.com
Grenoble Personal Computer Division  HPDesk - Martin CROOME / HP6300/K1
Technical Mktg - Online Support
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