Mike_Benna@mindlink.UUCP (Mike Benna) (02/09/91)
Here are a few more tidbits of information which I haven't seen
mentioned yet:
1) The Trident 8800CS chip set works fine in 16-bit mode, even with an
8-bit MDA card installed. I do not know how they do this but I can tell
you that it works fine. At one point I thought it was my motherboard
but since the Trident VGA cards works in 16-bit mode on at least 4
different motherboards I suspect it is the 8800CS which makes the
difference.
2) Many 16-bit VGA cards can be forced into 16-bit mode by setting a bit
in their extended VGA registers. For instance the Paradise cards
(PVGA1A and PVGA1B) can be set to 16-bit mode by setting bit 2 of port
$3CE, index $09. This renders the MDA card useless but the VGA runs at
full speed in 16-bit mode. This solution is far more preferable to the
hardware modifications I saw mentioned earlier.
3) Most 16-color graphics modes use the latch registers which are
compatible with the EGA. Since these latch registers are only 8-bits
wide, most VGA cards (even 16-bit cards) run in 8-bit mode when doing
any 16-color graphics.
Text modes and 256-color graphics modes almost always run in 16-bit
mode. Properly coding the alignment of your video memory writing can
result in a 2:1 increase in speed when using 16-bit VGA cards (believe
me - I've done lots of this type of optimization - it can make a big
difference).
---> Mike
--
---> Mike Benna, Vancouver, B.C., Canada
MindSpan Technologies Corp - Video Game Design and Development
UUCP: Mike_Benna@mindlink.UUCP or uunet!van-bc!rsoft!mindlink!Mike_Benna