Abit BX133, video, and I/O voltage

I recently replaced a BX133 board that was (literally) frying Radeon cards with a new BX133. The same CPU, memory, cards (except video card), etc. were used in both the old board and the new board.

The problem I'm having with the new board is that I have to crank the
I/O voltage *way* up (to 3.8V) to get any video with a 133 FSB. If I
set the I/O voltage down to the "recommended" 3.3 or leave it at the
default 3.5 while the FSB is 133, the box either boots with no video
output (monitor stays in "suspend" mode) , or doesn't boot at all. If
I set the I/O voltage to 3.6 or 3.7, the box boots but there is very
significant video artifacting, even in text mode (characters malformed
or disappearing on the POST screens, etc.) If I set it to 3.8, video
is OK but the box becomes very, very unstable in Windows (hangs upon
Windows loading, etc.) This happens with both a new Radeon video card
*and* with a Geforce2 MX video card. If the FSB is set to 100, I get
video with the usual 3.3-3.5 I/O voltage and the box is stable.

I'm using a PIII 1 GHz CPU (7.5 multiplier) and 768 MB Crucial CAS 2
PC133 SDRAM, for what that's worth.

I didn't have this problem with the old board before it went bad, and
many others here seem to have no problems with this configuration
despite it being less than optimal -- why am I having such trouble
with the new board? What else might be wrong?

-SC

Well chances are the card is having problems with the 2/3 AGP setting. I have the same board and while my computer boots up at 133FSB, I don't have USB mouse access. If I push my vcore to 1.95 then I have my mouse access but I still lose it eventually. Haven't actually tried pushing the I/O voltage more then 3.5

Anyway chances are with the high FSB and higher voltage, then your GPU is getting hot. Can try putting another HSF and AS on it and maybe run some fans across it but can't guarantee that's what is the problem.

OK, but...

- the Geforce2 MX worked fine at 89 MHz AGP with the old BX133, and Radeons are generally reported to work well (I had no problems with my old one before the power surge fried it...)

- it doesn't matter if the box has been off 12 hours in a cold room (I tried it), it just won't boot with video -- so temp can't be the issue.

I did try swapping the power supply with another one (both 250W) -- no change. I could try a 350W PS, I guess, but I doubt it will make any difference.

Everything save for the new Radeon and the mobo itself (CPU, RAM, NIC, drives, modem, sound card, TV card, power supply, case, that Geforce...) were the same with the old mobo and the new one -- they're in the same slots and all.

I'm beginning to think I have a bad mobo (not passing enough voltage on the AGP bus when at a high FSB?) and that I should RMA it. (For one thing, I think this mobo is an older rev -- it has the plain HPT 370 ATA100 controller, *not* the HPT 370*A* like my old one...)

-SC

Try the newer power supply. I use to have a Geforce II GTS on my board and with my 300w power supply it wouldn't always boot on the first try. Would have to power up twice before it got video. Switched to a 435w Enermax and never had the problem again.

Installed 350W PS...

and no change -- still the same problem, no video but box otherwise boots at 3.3-3.5 I/O voltage.

I'm more and more tempted to RMA the mobo, especially since it's the only thing that changed from before...but I can't live without it for several weeks (it's in my primary Windows box) and I don't want to buy yet another mobo...

-SC

Well you know it might have something with the AGP compliancy. According to Sandra the AGP on that board is only AGP 1.0. Most cards seem to require 2.0. Of course the old Geforce II card I had and the newer Geforce II Pro I have both supposedly needed AGP 2.0 yet they still worked on my board which is the same as yours.