Strange case of screen corruption

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The problems I am experiencing are quite troubling. When booting my
computer with a relatively good card (9800XT, FX5900, etc) the screen
will get corrupted almost instantaneously (in the BIOS Screen).
Sometimes if I'm lucky I can get to Windows, but it will soon become

By Corrupted I mean that it is nearly Impossible to distinguish what is
on the screen.

The system I have: Athlon XP 2600, 512 Meg RAM PC2700 Corsair, ASUS
A7V8X, GeForce FX5900.

First of all, I would like to say that the system ran fine for about a
year with the GeForce FX5900. The problems suddenly started to appear
for no reason.

This began about a year ago. There was a power failure and I was forced
to reboot my computer (something I never do). As soon as I pressed the
power button, I noticed that the screen was corrupted. So, I shut down
the computer for a couple of seconds, and then I tried to start it. The
screen appeared to be fine, and Windows booted as well, so I forgot
about the incident.

About one or two months later, the problem began to reappear after a
reboot. Fixing the problem was relatively easy. Letting the computer
cool down about 20 seconds seemed to fix the problem.

After a while, the screen corruption would happen every time I would
restart the computer. But still, it was fixable.

Suddenly, say about a couple of weeks later, the problem started to
occur in Windows, and the system was almost impossible to use. It would
require a reboot every 5 minutes.

I immediately thought it was the video card, so I took it to my friend
Bob s place. We tested it on his computer, which had a similar
configuration. The card ran fine for about 8 hours, running every game
or 3d benchmark we could find. This really surprised me since my system
is unable to run it for 5 minutes.

I returned home, and of course the problem was still there. I still
don't believe in miracles. So, I tried everything:

- Memtest 86: ran about 10 times, 0 errors.
- Tried running with 1 memory stick out of 2.
- Removing all PCI cards.
- Changing motherboards (tried an A7N8X, and a Chaintech with a VIA
KT400A chipset).
- Unplugging hard drives, cdrom, all removable media.
- Using another monitor.

Every test would yield the same result: corrupted graphics right when I
open Windows or open the BIOS setup.
So I tried to plug a very old card, a Radeon 7500. Strangely, the card
worked fine (I am still using it, and it's very slow).

The Radeon 7500 does run fine but it exhibits some problems. I did
notice some artifacts on the display, specifically some black
horizontal lines on the left of the screen. The lines appear when I
move my mouse near the  hot spot .
And when the computer is cold (shut it down for more than a minute) it
displays a lot of black horizontal lines, and the screen keeps
flickering. This happens for about 2 minutes then everything returns to
Aside from that, the system is very stable and I am capable of running
it for 20 days or more without rebooting.

Then I tried a Radeon 9800XT (which was tested and works fine). The
screen Instantly became corrupted on boot.

What the hell could cause the problem? The only things I haven't
changed are the following:

- The memory
Well it's Corsair, so it's not as prone to error as say a Generic
brand. But I have tried each module individually, and the same symptoms
appear. I would be really surprised that both memory modules blew up at
the same time (but it's possible).
AND I tested them with Memtest86. Maybe memtest86 cannot detect all
types of problems (but I really doubt that).

- The CPU
Why would the CPU be the cause of this if EVERYTHING ELSE works fine!
Maybe it can't handle AGP 8x? I don t know.

- The power supply
I have an ANTEC 430W. It might not be sending the right voltage to the
AGP card only?

- The case itself
The motherboard might be in contact with the case? Other than that I
don't think the case can influence how the computer runs.
But I did check for shorts when I reassembled the computer (on changing
motherboards), and there were none. So the likelihood of the case being
the culprit is very low in my opinion.

On a side note, my friend John who bought the Same GeForce 5900FX at
the Same time from the Same store has the Exact Same problem. He also
has a similar setup to me. Also, the card runs fine on his Pentium 4

So my question is this. What the Hell could be causing the problem? Has
anything similar happened to you? If yes, how did you fix it? If not,
do you have any idea what could be causing it?


Re: Strange case of screen corruption

On 4 Oct 2005 10:11:03 -0700, "Peter Carter"

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Often memory problems are not a hard defect in module(s) but
incompatibility due to bios or board design.  One can check
this by manually setting different memory timings, BUT, the
odds are quite low that such problems would reoccur on
multiple motherboards and never have errors in memtest86 on
(every) attempt.

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CPUs don't "handle" AGP, chipset does.  That your CPU works
find with 7500 video is a sure sign it isn't the problem.

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All of the 4 pin molex connectors merge into same common
rails inside the PSU.  The connector used for the video card
will have nearly same voltage as any other- perhaps a
trivially lower voltage due to the video card being a
significantly larger load than anything else running from a
single power lead per 5V & 12V, but still relatively it will
receive same voltage as anything else from power supply.

However, if your connector is loose fitting, it may result
in heating of the contact area and degraded conduction.
Examine the card's socket contacts and those of the power
supply plug.  If you have any doubts about them, try a
different plug and clean the contacts on the video card
socket as good as reasonably possible. (wouldn't hurt to try
that anyway).

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SInce the 7500 video card works, that's unlikely.  Since
it's corrupt even on cold boot, overheating of the card is
also unlikely.  I would suspect the power supply first even
though it's a decent name-brand.  FX5900 is a very power
hungry video card, and while Radeon 9800 Pro is a little
better, it's still no lightweight in that category.

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One thought that comes to mind is that your PSU may not have
sufficient 5V current, as most (maybe all) of the boards
you'd mentioned used 5V for CPU power except the P4 system.
It could be useful to measure 5V (and 12V, 3.3V for that
matter) with a multimeter at the ATX connector and at the
video card connector.  Ideally such a system config would
use a trustworthy PSU with a minimum 5V/3V combined rating
of at least 220W, but even then, eventually it could take
it's toll.  You might open up your power supply (with AC
disconnected for at least a few minutes first) and examine
the interior, particularly check the output capacitors (near
where the wiring harness connects to the circuit board) for
signs of failure, domed tops or swelling, leaky residue or
even a spot where a capacitor "used" to be but is now only a
bit of paper and foil loose inside.  Just don't supply ac
power by plugging it in  with the cover off unless you are
confident in your ability to do so safely.

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Some common things to try are bios settting like disabling
sideband addressing, fastwrites, and reducing AGP rate from
8X to 4X.  I have an FX5900 that didn't need any of these
settings changed but they are relatively quick and easy,
"free" things to try.

Re: Strange case of screen corruption

Thank you for the support Kony, I appreciate it.

I will attempt to verify the power supply. I'll post back updates if I
am able to fix this!

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