unmeaty
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As the title states I have two 980Ti hybrids. One is a reference card with the AIO added (1000Mhz bc) and the other is a factory hybrid with the base clock set at 1140Mhz.
I had two reference AIO hybrids in SLI and had good luck overclocking them. I used MSI AB and got boost clocks at 1.5Ghz with 8000Mhz effective memory without adding voltage, temps around 45C-49C.
One of the cards died (zapped by a case ground fault, very sad) and I got another hybrid to replace it. This one has the higher factory clock.
So I figured once I put them in SLI the higher clocked card would sync to the lower speed and I could OC from there, but that hasn't happened. I've had some crazy results, Firestrike crashes more often than not.
What I'm unclear on is whether or not I should be syncing the OC offsets or setting them separately to match clock speeds. Say if I have them synced and set the clock speed to +200, does that set the target at 1200Mhz for both since the lowest clocked card has a 1000Mrz base? Or does it set the higher clocked card to 1340 and it just dials down during a 3D application to match the other, or...? It's confusing.
My bm results have been mostly crashes. I'm upgrading my power supply tomorrow. I don't think that's the problem - I have a 1000 Watt P2, I would think that should handle it - but I do have a lot going on besides the GPUs. A liquid cooled, overclocked CPU, OC'd RAM, many USB peripherals, two VR headsets, high end sound card, 7 (!) hard drives.
I'm getting a 1600 Watt P2. I can't imagine any 2-way SLI setup in the world that won't support with room to spare.
But yeah, the OC questions. If anyone has some advice on overclocking GPUs with different clock speeds I'd appreciate the feedback.
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Zuhl3156
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Re: Overclocking advice needed for two 980Ti hybrids with different clock speeds
2016/05/26 07:48:22
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The only way I have found any kind of stability with mismatched clock speed was to 'unsync' the video boards and OC each one independantly so the end result was that they both ran at the same speeds under load. Having the faster card's clock speed lowered by the other video board caused me a lot of crashing in games and benchmarks. Many will argue that running SLI with mismatched clocks is OK but it never worked for me.
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DeathAngel74
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Re: Overclocking advice needed for two 980Ti hybrids with different clock speeds
2016/05/26 07:53:03
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+1
I would unsync them. Run them both at the same clock if they can both run at 1506.5/8000 independently.
Carnage specs: Motherboard: ASUS ROG STRIX X299-E GAMING | Processor: Intel® Core™ i7-7820x | Memory Channels#1 and #3: Corsair Vengeance RGB 4x8GB DDR4 DRAM 3200MHz | Memory Channels#2 and #4: Corsair Vengeance LPX Black 4x8GB DDR4 DRAM 3200 MHz | GPU: eVGA 1080 TI FTW3 Hybrid | PhysX: eVGA 1070 SC2 | SSD#1: Samsung 960 EVO 256GB m.2 nVME(Windows/boot) | SSD#2&3: OCZ TRION 150 480GB SATAx2(RAID0-Games) | SSD#4: ADATA Premier SP550 480GB SATA(Storage) | CPU Cooler: Thermaltake Water 3.0 RGB 360mm AIO LCS | Case: Thermaltake X31 RGB | Power Supply: Thermaltake Toughpower DPS G RGB 1000W Titanium | Keyboard: Razer Ornato Chroma | Mouse: Razer DeathAdder Elite Chroma | Mousepad: Razer Firefly Chroma | Operating System#1: Windows 7 SP1 Ultimate X64 | Operating System#2: Linux Mint 18.2 Sonya (3DS Homebrew/Build Environment)
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unmeaty
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Re: Overclocking advice needed for two 980Ti hybrids with different clock speeds
2016/05/26 08:10:29
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Excellent, thank you. Once I get the new PSU installed I set them both up at the same clock speed and go from there.
I appreciate the feedback, this is the first time I've ever had an SLI setup with 2 different clock speeds.
Oh, and something strange - when I removed the newer card, apparently MSI ab remembered the previous core offset even though it wasn't showing it. I had to reinstall MSI to reset it. In other words, a +250 offset was being applied on top of the previous offset, and the results were what you'd expect. Took a while to figure that one out.
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Zuhl3156
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Re: Overclocking advice needed for two 980Ti hybrids with different clock speeds
2016/05/26 08:18:56
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Another thing I have found is that if you boost the volatge on the slower card it will boost the Core Clock without making any other changes. My slow board had an ASIC of 65% while my fast board had an ASIC of 79.3% Boosting the voltage on the lower ASIC 980 gave me matching speeds.
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unmeaty
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Re: Overclocking advice needed for two 980Ti hybrids with different clock speeds
2016/05/26 09:11:13
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How do you measure the quality of your ASIC? GPU-Z? Is that accurate?
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Zuhl3156
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Re: Overclocking advice needed for two 980Ti hybrids with different clock speeds
2016/05/26 09:20:48
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Yeah, right-click in the upper border and select 'Measure ASIC' from the drop down menu.
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Sajin
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Re: Overclocking advice needed for two 980Ti hybrids with different clock speeds
2016/05/26 11:54:59
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Zuhl3156
Having the faster card's clock speed lowered by the other video board caused me a lot of crashing in games and benchmarks. Many will argue that running SLI with mismatched clocks is OK but it never worked for me.
Never had a problem myself.
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Zuhl3156
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Re: Overclocking advice needed for two 980Ti hybrids with different clock speeds
2016/05/26 12:09:54
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Sajin
Zuhl3156
Having the faster card's clock speed lowered by the other video board caused me a lot of crashing in games and benchmarks. Many will argue that running SLI with mismatched clocks is OK but it never worked for me.
Never had a problem myself.
Some guys have all of the luck!
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unmeaty
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Re: Overclocking advice needed for two 980Ti hybrids with different clock speeds
2016/05/26 23:10:34
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Just an update. Got the new PSU installed, it's beastly. I should be good for the next ten years.
Anyway the method you guys suggested worked well. I set the profiles separately for each gpu and they work great, both sustain a 1506mhz boost with 8001mhz effective memory clock, with minimal voltage. I had to fine tune each one to get them perfectly in sync, voltage can pump up the clock post the offset as was suggested.
In the end I got a very stable sli oc, enough to run anything on ultra at 3440px1440p.
I appreciate all of the advice.
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toyking22
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Re: Overclocking advice needed for two 980Ti hybrids with different clock speeds
2016/05/26 23:43:16
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i had to unsync mine to get them at the same clock speeds,, 1 still rarly goes down to 1498 here and there from 1500
Cpu= I7-9700k Cpu cooler= Nzxt Kraken x62 GPU= Evga Hybrid 2080 ti Motherboard= Asus Prime Z390 a (dont recommend) Ram= G.SKILL TridentZ RGB Series 16GBSsd/Hdd Samsung 970 pro 2T / Intel 660 1t Monitor= Gigabyte M28U 144Hz 28" 4K Power Supply= EVGA SuperNOVA 850 PQ
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SuperConker
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Re: Overclocking advice needed for two 980Ti hybrids with different clock speeds
2016/05/27 01:00:53
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SuperConker
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Re: Overclocking advice needed for two 980Ti hybrids with different clock speeds
2016/05/27 01:00:54
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Since both of your cards seem to be identical (reference boards with Hybrid coolers) you could try flashing the Bios of the card which has the stock 980ti Bios, with the Bios from the overclocked Hybrid card. This should take care of any SLi issues regarding different clock speeds (be sure to create a backup of the original Bios before flashing it with the Hybrid Bios).
post edited by SuperConker - 2016/05/27 01:20:18
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Zuhl3156
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Re: Overclocking advice needed for two 980Ti hybrids with different clock speeds
2016/05/27 05:14:16
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ASIC has more to do with the lower clock rates than the BIOS. Svet at MSI Forums gave me matching VBIOS for my boards but the lower 65 ASIC still would not give me higher clocks without adding voltage. I could boost it farther, up to +185, but the clocks didn't reach as high as the other 79.3 ASIC board at +145.
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