Phenom II Meets Dry Ice
Months befores AMD Phenom II processors hit retail shelves the marketing department at AMD was in hard at work showing both the media and the enthusiast community and that Phenom II processors were overclocking giants once again. The original AMD Phenom processors were sensitive to temperature changes and once you got sub-zero they often had negative scaling when it came to overclocking. With the vast majoirty of Phenom processors hit a wall at -20C the most extreme overclockers were out of luck. AMD has done a great job at getting the word out that Phenom II is a new and improved processor, but how do these new Phenom II processors overclock with extreme cooling? AMD showed us that the temperature bug is long gone by running a AMD Phenom II X4 processor at 1.95V and at below -190C, but what can we pull off on our own test bench? This weekend we purchased ten pounds of dry ice along with some Acetone to see what we could get a pair of Phenom II socket AM3 processors could do on the ASUS M4A79T Deluxe motherboard.
The AMD Phenom II X4 810 processor has been floating around the test bench for over a month now and I've maxed it out with after market air coolers at 3.82GHz on the ASUS M4A79T Deluxe motherboard and 3.84GHz on the MSI DKA790GX Platinum motherboard. Since both boards feature different CPU sockets and chipsets it is fairly safe to assume that this is the highest overclock that this processor can get with air cooling.
With the test system locked and loaded with dry ice we waited till the temperatures leveled off around -45C on the sensor located next to the CPU socket and fired up the system. Since the goal to to see how high we can get we enabled the 'overvoltage' jumper to get higher voltage options in the ASUS M4A79T Deluxe BIOS. The Phenom II X4 810 is a locked multiplier and has a few limitations (locked Multipliers, locked VID voltage codes, you can adjust voltage only with OFFSET and that is always limited) and is honestly not ideal extreme cooling like dry ice. Since we have the processor and have overclocked it so many times before we wanted to see what it could do anyway.
With the 'overvoltage' jumper enabled the CPU Voltage max went from 1.45V to 1.65V on the Phenom II X4 810 processor, which should help the processor reach a higher overclock than we were able to get on air.
Keeping an HT Link of and CPU/NB frequency ~2200MHz the highest I could get into Windows Vista Ultimate 64-bit with any stability at all was 4069MHz. Running with a 313MHz HT reference clock is impressive, but being limited to 1.65V on the CPU Core and having no multipliers above 13x really hurts overclocking.
Dropping the HT Link down to under 1000MHz I was able to push the last couple MHz out of the processor and hit a 313MHz HT reference clock, which puts the AMD Phenom II X4 810 processor at 4095MHz. This is roughly 260MHz higher than our best on air cooling, which is not too impressive for dry ice cooling.
Let's move on to the AMD Phenom II X3 720 Black Edition processor to see if the unlocked processor fairs any better on the same system.
Phenom II X3 720 BE Overclocking
With a new processor installed in the frosty ASUS M4A79T Deluxe motherboard we kept our fingers crossed that something higher than 4.1GHz could be reached.
The AMD Phenom II X3 720 Black Edition processor faired much better with Dry Ice cooling since the multiplier could be increased and the CPU votage was able to go up to 1.90V in the BIOS since ASUS allows for higher voltages on the Black Edition processors. After playing around with the HT reference clock frequency and multiplier we managed to reach 4590MHz from the 2800MHz processor. This is 200MHz shy of a 2GHz overclock and is what we expect from Dry Ice cooling!
After the Arctic Silver thermal compound thawed out enough for the pot to be removed there was a layer of ice around all around the CPU socket, but the motherboard was fine even after running with all the ice buildup. That means that we will have to revisit dry ice cooling down the road, but for now we are out of dry ice and have other articles that need to be written! It is confirmed that AMD Phenom II processors don't have a cold bug as we were running around -50C, with no problems at all. Looks like the old overclocking friendly AMD processors are back and it is likely a fair number of AMD enthusaists will be back as well.
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