i7 Hyperthreading causing Render Artifacts - Ruh Roh

[wwswimming]

http://forums.cgsociety.org/showthread.php?f=6&t=828690

"Rendering on Core i7 creates noise artifacts, looks fine on Core 2 Duo"

"i'm doing a test render right this minute with HT turned off, its almost done so will post back but I think it is HT releated. I noticed that sometimes MR would give me 13 or even 14 buckets sometimes when it should only use 8 with HT. Now it uses 4, one for each core (no HT) and fingers crossed."

"Yup, it was Hyperthreading causing the artefacts within the render frame.

Thanks for helping."

where does this get fixed - in the CPU, the Motherboard, the OS, or the application ? the guy's using 3D Max & had to turn off hyperthreading to get a decent render.

he's using Mental Ray, which renders in 'buckets' (a square section of the screen about 40 pixels x 40 pixels). with HT on, the buckets get mixed up, resulting in some Salvador Dali-esque outputs.

they've discovered a new art form !

 

[Rubycon]

We need more widespread results to see if this is a hardware flaw.

I had a QX9650 that was artifacting because it was o/c too high and completely stable in every other stress test out there for weeks even! Eventually stability came down where it would only pass LinX at default clock speed but still artifact.

So then we put it in another motherboard and it was able to o/c without problems. Interestingly enough another QX9650 was perfect in the motherboard that was giving issues with CPU1!

Sometimes this stuff makes me want to throw it all to the fishies and go back to using an easel. 🙁

 

[zsdersw]

I suspect it's a problem that is application-specific and will need to be fixed by altering the application.