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| by 3oh6 | June 9, 2009 | |||||||||||||||
| Last Stop: Liquid Nitrogren National Park  The best part of any summer vacation road trip is the last stop of the journey. Partially because a part of you just wants to get home and you are only one step away from that, the other part is because it should be the best stop of the trip. For us on this road trip, getting home has nothing to do with it. Liquid Nitrogen National Park is the ultimate stop for any overclocker and once you go, you never want to leave. With temperatures as cold as -196C, Liquid Nitrogen National Park can get frighteningly cold, but usually something stands in the way.   As was the case in previous locations, we have a couple different setups that we will use for the overclocking. Our SPi setup makes an appearance again, as does the single GTX 295. The only difference from previous locations is the processor cooling. Strapped to the Core i7 975 EE's back is a MMouse Rev3 all copper liquid nitrogen cooling pot while insulation remains the same as it did for Phase Change City on the motherboard. That is the beauty of kneaded rubber eraser, it is great for -40C and just as good for -90C. One major addition to our stop in Liquid Nitrogen National Park is the addition of four lovely red cards...seen below.   It is no secret, the EVGA X58 Classified has four PCI-E 16X slots, so we figured that we should fill them. Swapping out the stock cooler on one of the cards allowed all four to fit with ease and after wrangling with ATI's lovely (can you hear the sarcasm folks? -Ed.) driver package for a while, we figured out how to get these four cards working in CrossFireX. This is obviously where the second PSU we listed earlier comes into play as the single Corsair HX1000W simply can't handle this many video cards. Needless to say, we have probably the most powerful benching platform available right now...for most benchmarks anyway. Just remember that 3DMark Vantage still falls horribly behind NIVIDA video cards, even with a fourth HD4890. Let's first take a look at the results we were able to pull off with our standard GTX 295 setup with a full 30L dewar of LN2.
Getting the full suite of benchmarks done with a single 30L dewar of liquid nitrogen really was a challenge. Because of this, we weren't able to full maximize each and every benchmark. If we were able to spend a full day and full dewar on each benchmark, we could definitely squeeze a few more clocks out of most of them, but the results we achieved are nothing short of excellent. We found the optimal operating temperature with this chip to be around -75C for 3D and multi-core benchmarks. SuperPi liked to run a little warmer around -60C which isn't un-common. Again, every chip is going to be different and you have to really learn what your particular CPU likes when cooling with LN2.  One interesting roadblock we ran into with this processor during our LN2 benching was the fact that we were getting a "cold boot" issue which is similar to the "cold bug" we explained earlier. Only in this case the issue only affects the ability to boot after a restart or shut down. We found that between about -40C and -70C, our processor wanted nothing to do with booting, especially after a power off. Going colder than -70C seemed to completely cure the issue. I have personally never experienced a processor that acted like this and no other Core i7 or C2D chips I have benched have presented a "cold boot" hole. Needless to say, it took a bit of time to figure this out but once we did, it was business as usual. This is just part of the fun benching at sub-zero temperatures considering we are operating the processor well out of its specified environment both in temperature and voltages.
Speaking of struggling to overcome hurdles, if you want to drive yourself nuts, just put four HD4890's together in an EVGA Classified and try to bench with even just the CPU under LN2...all we can say is good luck. ATI drivers really made this a challenging experience but again, time and persistence allowed us to really hit some great results in 3Dmark 05 and 3DMark 06. The 3DMark 03 result is not even close to what it should be but in order to maximize 3DMark 03 in Windows 7, it takes a rather delicate process of driver installation and OS setup. We already started running out of LN2 in this massive 14 hour session and couldn't get a 3DMark 01 result completed, okay okay, so I forgot about 01...wanna fight about it? So getting a solid 03 result just wasn't in the cards. Even still, cracking 46K in 05 and 34K in 06 is no small feat and something we were quite pleased to manage. | |||||||||||||||
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