Weird OC SLi "issue" !

[Gripen90]

This behaviour baffels me a bit since I have never experienced it with SLi before.
Since 2009 I regularly have run SLi with different clocks speeds and the nVidia drivers have always allowed the cards to run at their individual speeds. I remember nVidia releasing the drivers and pointing out that individual clocks speeds were now supported so NO downclocking !.

However yesterday when I wanted to SLi my Asus GTX 980 Strix with my Gigabyte GTX 980 G1 in SL I noticed something very odd !.
I OC'ed both cards via MSI Afterburner. I OC them individually and not set "sync'ed" in AB settings.

I expected the Gigabyte GTX 980 G1 to boost higher on the GPU core since it's naturally clocked higher than the Asus card - 1228mhz vs 1178mhz.
So I knew the max OC for my Asus card and set it to 1330MHz GPU and 1950MHz Vram.
The Gigabyte card I set to 1350MHz and 1950MHz just to see if the G1 would boost past 1500Mhz.

Now the odd stuff happened ! Regardless of running games or benchmarks the Gigabyte G1's boost clock would always match the boost clock of the Asus card of 1443Mhz !. I tried OC'ing the G1 to 1360MHz core and check again but still it ran 1443Mhz just like the Asus card.

I thought that was weird so I tried OC'ing my Asus card a bit more to 1343Mhz and the Asus boost clock would be 1453MHz. And now the Gigabyte G1 was running 1453MHz too !!. However I noticed my Asus card began to produce green checkerboard patterns some times, so I took it back to the rock solid 1330MHz settings.

So I have NEVER EVER experienced this before ! The Gigabyte G1 automatically limits it's Boost clock to match the Asus Strix.

I have run different manufaturer cards many times and last I had Palit GTX 780 Super Jetstream and Inno3D GTX 780 Ichill HerculeZ X3 Ultra DHS Edition cards running SLi and both ran at their max individual boost clocks !.

Has something changed in the drivers or is it the Maxwell structure ?

Right now I run both cards at 1330MHz GPU and 1950Mhz vram and their Boost clock is rock solid at 1443MHz and never changes (there is no point in OC'ing the Gigabyte any further due to the above symptoms).

However I cannot help feeling that my OC is being held back by the Asus card , so I'm considering replacing it with another Gigabyte G1.

 

[Gripen90]

Just got confirmed in another forum that it's not my machine behaving strangely. It a Maxwell "feature" not present in the Kepler cards.

 

[Sasahara]

I doubt it would make much off a difference as I would expect performance would be limited by the slower card irrespective of the clock speeds of the individual cards.

 

[Ace Modder]

I had exactly the same with a G1 980 and an MSI OCV! 980 (reference in design)

I was find that the G1 was going up to 1443mhz but the MSI stock speed meant it was lower, but the strange thing was the actual on the MSI card was lesser than the G1 and the vcore on the MSI card was not going over 1.04v most of the time, but the G1 was going up to 1.256v

After a few days of giving up with it, as I th=ough the MSI was just not liking SLI and being slower, and the MSI card was not boosting up to the max speed I set it to do ( I ran both cards at +120 on the core and +500 on VRAM)

I decided to try something different and set the +speed on the GPU of the MSI to +196 (but leave the G1 at +120 so they matched exactly on max speed) as the stock speeds were 70mhz different, and now both cards are now doing a nice speed of 1512mhz and the vcore is about 1.23-1.26v on both cards, much closer and both are doing the same speeds now.

It was almost as if the the system was not giving full vcore juice to the MSI card because it wasnt getting to the same speed as the G1 card, but now they are both boosting the same, the vcore is about the same on both cards.

Now I'm really happy Maybe your G1 card is not getting the right vcore (like my MSI card) amount and thus is not boosting up enough?

P.S. I was going to sell my MSI card and buy a G1 and a new waterblock for it, but now I've got my MSI card working great I am not going to bother. (that reminds me i need to close my for sale thread on MM for the MSI card)

 

[Gripen90]

*double post*

 

[Gripen90]

I had exactly the same with a G1 980 and an MSI OCV! 980 (reference in design)

I was find that the G1 was going up to 1443mhz but the MSI stock speed meant it was lower, but the strange thing was the actual on the MSI card was lesser than the G1 and the vcore on the MSI card was not going over 1.04v most of the time, but the G1 was going up to 1.256v

After a few days of giving up with it, as I th=ough the MSI was just not liking SLI and being slower, and the MSI card was not boosting up to the max speed I set it to do ( I ran both cards at +120 on the core and +500 on VRAM)

I decided to try something different and set the +speed on the GPU of the MSI to +196 (but leave the G1 at +120 so they matched exactly on max speed) as the stock speeds were 70mhz different, and now both cards are now doing a nice speed of 1512mhz and the vcore is about 1.23-1.26v on both cards, much closer and both are doing the same speeds now.

It was almost as if the the system was not giving full vcore juice to the MSI card because it wasnt getting to the same speed as the G1 card, but now they are both boosting the same, the vcore is about the same on both cards.

Now I'm really happy Maybe your G1 card is not getting the right vcore (like my MSI card) amount and thus is not boosting up enough?

P.S. I was going to sell my MSI card and buy a G1 and a new waterblock for it, but now I've got my MSI card working great I am not going to bother. (that reminds me i need to close my for sale thread on MM for the MSI card)

Mmm no that wasn't really my issue that the cards wouldn't "boost" to the same speeds.
The issue is/was that the Max Boost clock on the 980 G1 Gaming is limited to the Max Boost clock of the 980 Strix. Only if I OC the Strix further, then the boost of the G1 will follow. With the older Kepler cards each card would boost to their individual max in SLI. Appearently this is not the case with Maxwell cards, their max boost clocks follow in sync.
My Asus Strix is a dud overclocker, as soon as it get over 1453MHz boost clock it glitches