[comp.sys.ibm.pc.hardware] Wierd Problem

lee@infonode.ingr.com (Lee McCain) (02/19/91)

Hi, Netlanders:

I have a kinda wierd problem.  I have a 386/33mhz w/64k cache machine with AMI
BIOS and SIS chipset.  Also my video card is a Tseng ET4000 based card with
1mb.

My 16-bit bus is running at 1/3 of the system clock which should be about 11.13
mhz.  The video card specs. state that it can be run up to 12mhz.

What happens is that the video looks like it's vibrating.  It's almost like you
can see the monitor scanning.  By the way, the monitor is a Viewsonic 4, Multi-
Scan.  

Anyone have any ideas??  The monitor works fine on another system.  I also put
the card in a 25mhz system along with my monitor, and it worked fine.  The
25mhz system was a C&T Chipset and the bus was running at ATBUS (?) setting in
CMOS which should be 8mhz.

If I set my bus to 1/4 of the system clock (8.35mhz), I still have the problem.
The wierd thing is that I can press my turbo button, cutting the system clock
to 16.7mhz and everthing works fine--no vibration, waves, etc.

The motherboard vendor says it's the bios on the video card.  Of course, the
video card people are saying that it appears to be the motherboard.

Ideas....????

Regards,
Lee McCain

...!uunet!ingr!se_bbs!lee

----or----
lee@ingr.com