question for those, who own GTX590...

[Timmaigh]

i just found out quite unpleasant fact i was not aware of...

during rendering i always used to overclock the card to go faster than its default clocks (607MHz), as it clearly improved the Megasamples value, therefore it supposedly rendered faster...
today i did the same, OCed the card to 750 Mhz (1500 shaders, 3900 vram), which improved the Ms per second in the actual scene from 1,89 at default clocks up to 2,32...

BUT

after few minutes of rendering this value would drop back to 1,86 and i can hear the fan going less louder.... clearly the card is throttling, even though GPU-Z still reads 750 Mhz.
I tried it with lower overclocks, as 750 is quite a lot... but it would happen at 700/1400/3800 as well, rendering starts at 2,12 Ms, but few minutes down the road drops to that default clock value...

and now i have to wonder, if this was always the case, i just failed to spot it, or the card is somewhat degrading after year and half of use...or whatever is the reason...therefore can someone, who owns the card try this out, and confirm, whether this happens to him as well or not...

thanks

[glimpse]

What is Your cooling solution? =)

[Timmaigh]

What is Your cooling solution? =)

Air cooling, the reference solution, as all the gtx590s were, as far as i know. No water or anything fancy. Additionally i have 2 14cm Noctua fans and 3 Fractal Design Silent series fans inside the case to help with the airflow.

[glimpse]

With stock cooling I wouldn't even consider OCing =) if You don't want to burn Your cards =).. It's not some game, where You don't need GPU runin' 100% all the time..for compute intensive tasks..without custom cooling loop with water you'll see almost none of the benefit just burn Your card faster =).. GTX 590 produce a lot of heat..in stock frequencies..- that's one of the reasons why it goes out. Underclocked (compared to 580) out from factory door =)..

If I were You I would leave defauts =) unless You get some WC blocks on it =)

Cheers

[Timmaigh]

Actually, you would be surprised, but Octane is more forgiving than games... on some games, like latest Call of Duty, if i leave the card OCed at 700 MHz, even without multi-GPU on (means just one of the GPU cores is running the game, the other is idle), the game would eventually crash/freeze and the only thing left to do is the hard reset of entire computer... similarly StarCraft 2. But not Octane, i was using it at 700 Mhz both GPUs on since i got the card, and i dont recall crashing it once....now the possible reason for that is that the card throttled itself like what i suppose is happening now, without me noticing...yet that is still better situation IMHO than total crash...

Additionally, i dont think there is any risk in OCing the card, unless you play around with voltages, but i am not that rich to do that . Anyway, just increasing the frequencies, at worst you can make the card unstable or to make the in-built protection against damage to kick-on... thats why the card throttles. OFC, it can always burn out, but that can happen regardless of the OC, if you are not lucky...

Addendum:

I tested this with the trench benchmark scene and it does not happen there. I left it rendering for 30 minutes and at 750 MHz it keeps the 5,5 Ms value throughout... no drop at all (at default 607 MHz clock it was about 4,7 Ms).... conclusion: it is somehow related to my scene. Either is more performance taxing than the benchmark (what would be understandable), thus causes the card to throttle...or there is some other issue.

[glimpse]

Yeah, You're right about heat, stability & voltages =) - quite the same as for CPUs =)

P.S. nice observation =)

what kernels You're using for these scenes?..
Maybe that's somehow conected? Maybe this effect is only on certain type of scenes as You say..

[acc24ex]

- decided not to go down that route, after a few runs, since the temps go over 90 C with an additional fan on top, that 10% boost is just 10% at the expense of a system burn and crash - and you get crashes even without that