DX9 Not Completely Backwards Compatible?

[Test]

I'd like to find out if others have experienced this same
problem:

+Install a clean OS of either 2K Pro or Xp Pro
+Install all necessary drivers
+Install DX9
+Install game requiring DX8.1a

Result: Games requiring DX8.1a consistently crash or cause
reboots.

+Repeat steps above on same hardware, except stay with
Directx8.1

Result: No problems with games

My setup:

+Asus a7n8x Deluxe
+ATI Radeon 9700 Pro
+2xCorsair 2700C2 512M (in dual ddr mode)
+ATA133 hard drive
+All current drivers (except for ATI Catalyst, 3.4 instead
of 3.5 drivers)
+400W Power

I initially tried replacing every part in my system. Tried
with one stick of memory. Tried different memory brands.
Then I talked to Asus and ATI support, tweaked various
settings in the bios affecting video cards. Nothing
worked. I consistently crashed to desktop or rebooted when
running Directx8 D3D games. It wasn't until I wiped my
system, installed everything clean with DX8 that my
problems stopped.

I checked some game logs and it appears to throw errors
that may possibly cause these problems. You would think it
was the game right? Possibly, except when I repeat the
same set of steps causing the crash, except with DX8.1a,
the games run fine.

I could only conclude that DX9.0a was not transparent in
its backward compatibility, atleast when used in
conjunction with ATI Radeon 97XX and Asus A7n8x cards. I
have heard of other people having similar problems. Can
anyone confirm/validate/explain my problems?

thanks.

 

[David Jones]

I haven't had this problem at all. I play a variety of
games that want anywhere from DX 6 to DX 9 (including DX
8 and DX 8.1a).

What games are you seeing this on?

 

[Test]

Two questions for you:

1) Do you have a DX9 Card (such as Radeon 9XXX or Gfx)
2) What is your hardware set-up like?

One game I was consistently able to reproduce this
behavior on was Mythic's Dark Age of Camelot. I talked to
their support and they tell me they don't support DX9
(understandable...DX9 wasn't available when they released
their game). However this shouldn't matter correct, since
Dx9 should be fully backwards compatible? Had this happen
on a couple of others as well (such as Unreal 2).

thanks.

 

[EGMcCann]

Nope, not here. Freshly built system, too. And I've got games requiring
everything from DX3 on up.

 

[Mathiau]

for one you would be better off with ANY other catalyst suit beside the
3.4 - they are known for the most issues, go with 3.5's or 3.2's. or lower.

Mathiau.