On 12 Dec 98 at 8:29, Michael Beechey wrote:

> Dear old timers who remember this stuff: (I think we're talking about
> Hardware = BIOS?)
>
> I have 2 old 256k/512k VGA cards, no drivers, that I am shuffling
> around in old machines. I needed to move the 512 to a DX4 to get
> 256 colors in Win95b.
>
> The 256 card works fine in one machine (DOS>and Win95b) but
> hangs in some progs in another (DOS 6.2)  The BIOSs are different
> in both machines, I don't know anything about Video Shadow or
> Cache, but trying the different settings I haven't resolved the
> problem, if that is the solution.


Shadow
  The ROM Video BIOS is on the card.  Especially if this is an ISA
card, the expansion bus represents a bottleneck between the CPU and
these instructions, which can slow down video operations.  Shadowing
copies this ROM into motherboard RAM at startup, from which the CPU
can read instructions as fast as from anything else in main RAM.  I
would enable this unless you are running Windows NT.  [In theory, NT
never uses the ROM, so this would be a waste of memory.]

Caching
  If you don't enable shadowing, you can still allow instructions
fetched from this ROM to be held in the cache, so that repeated
sequences do not incur the access penalty repeatedly.  I would always
enable this.  [Only code that is used can ever get cached; if NT
never uses it, who cares?]

David G

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