Random, Garbled text on screen after prolonged testing

[lockon]

I have a very strange issue that I thought may be due to bad RAM but after extensive testing seems to be something else... but I have nowhere else to turn so I thought I'd ask the experts here: A user reported that their PC would randomly go from normal operation to a garbled screen like this:



So I ran MemTest and I found a faulty RAM module. However, during MemTest, the screen ended up looking like this:



So, I replaced the memory and reran the test... the memory passes, but the screen still ends up looking like above (minus the red line)!! I ended up replacing almost every single part to test and the problem still exists. Does anyone have any idea what is going on?

Here are the relevant specifics:

GIGABYTE GA-B75M-D3H [replaced with spare & retested - same result]
Intel Core i5-3470 Ivy Bridge 3.2GHz [not replaced]
PNY Optima 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1333 [replaced with spare & retested - same result except no mem fault]
Thermaltake 600W [replaced with diff ps & retested - same result]

Any help is appreciated.
Thank you
Sunil

[David (PassMark)]

You are using MemTest V4.0. Which is an old release.

The behavior you are seeing is the test algorithm writing test data into the video display buffer. This should not happen as this memory region should be off limits for testing.

If this happens in Windows as well, then it points more to a BIOS issues. The BIOS should be flagging the memory ranges of that are free and available for use as main RAM.

Can you try the testing again with V4.2. and see if you get the same behavior.
Can you also see if there is a BIOS update available for the machine.

[lockon]

Can you try the testing again with V4.2. and see if you get the same behavior.
Can you also see if there is a BIOS update available for the machine.

Thank you. MemTest 4.2 test underway, BIOS update is queued. Current BIOS is V4 and latest is V13

Update to follow.

[lockon]

Well, I think you nailed it

First, MemTest 4.2 did NOT produce the same problem even before the BIOS update. In a way, I'm very glad that 4.0 brought this issue out.

I updated the BIOS and reran V4.0 and there was no issue, so the BIOS was the issue.

Now I have put back the original motherboard and updated it. Test is under way!

Thank you for hints, much appreciated!!!
Sunil

[lockon]

Just a final update:

I reran using MemTest 4.2 with BIOS updated and known good RAM - 4 passes all went well. I reinstalled the faulty RAM and reran with 4.0 - 4.0 showed errors and also had the screen garbled. So, I reran with 4.2 and it showed the errors on the RAM but didn't garble the screen...

not sure what it all means with regard to the versions of memtest (or if anyone cares!), but maybe someone finds it useful.

Sunil

[David (PassMark)]

I think the conclusion has to be is that some bugs were fixed between MemTest86 V4.0 and V4.2 that prevented the display's memory being overwritten.