AMD Phenom II X4 940 & 920: A True Return to Competitionby Anand Lal Shimpi on January 8, 2009 12:00 AM EST
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Hooray, AMD is Overclockable Again
Since the introduction of the B3 stepping Phenom that solved the TLB bug (along with improved yields), overclocking a Phenom has been a fairly painless process. This is especially true with the Black Edition series and a well designed motherboard based on the 790FX, 790GX, or 780a chipsets. While the Phenom has not offered the same overclocking headroom as the latest Penryn processors that typically offer a 1GHz improvement on the middle to upper range processors with air-cooling, it is not uncommon to see the Phenom BE series offering a 600~800MHz improvement in clock speeds.
AMD has proven in early demonstrations that the Phenom II x4 will offer overclocking headroom similar to the Penryn series. Early production sample processors have clocked anywhere from 3.9GHz on air to 4.4GHz on water and all the way up to 6.3GHz on LN2. We have matched their results on air-cooling and been impressed with the potential headroom offered by the new 45nm manufacturing process on extreme cooling setups. In fact, the latest retail steppings that AMD displayed this past week showed significant improvements in overclocking headroom compared to the press samples we utilized. Our 940 topped out at 3.9GHz, which is not bad, but after reviewing AMD’s results and seeing some early retail numbers on the forums, the expectation level for air-cooling is now set to the 4.1GHz range with the 920 hitting 3.8~3.9GHz on the right motherboard.
We have retail processors arriving shortly for additional overclocking tests (we will push HTT/NB settings); in the meantime, we have some interesting numbers to present with our press samples. In our overclocking tests today we are utilizing the Phenom II X4 940, Phenom 9950 Black Edition 125W, Core 2 Q9550, and the Core i7 920. Besides having a strong processor, a well-engineered motherboard, premium memory, excellent cooling, and proper power supply are all essential elements in obtaining stable and high clock speeds when overclocking.
With that in mind, we are utilizing the DFI LP DK 790FXB-M2RSH (790FX), ASUS Maximus II Formula (P45), and DFI LP UT X58-T3eH8 (X58) motherboards for testing. We also tossed in the Corsair HX1000 power supply along with memory from Corsair and G.Skill featuring their TR3XGG1600C8D 6GB DDR3-1600 and F2-8800CL5D-4GBPI DDR2-1100 4GB kits respectively. The balance of the test system consists of a WD Caviar Black 1TB HD, Blu-ray drives from Sony and LG, Vista 64 Ultimate, and our ABS Canyon 695 case.
In a twist from our normal overclocking results, we decided to utilize the retail air-coolers from Intel and AMD to provide a more realistic out-of-box experience when overclocking. We based today’s test results on how high we could overclock on stock voltages and then by increasing voltages until we ran out of cooling headroom with the retail coolers.
|Processor||Highest Overclock (Stock Voltage)||Highest Overclock (Overvolted)||% Increase over stock||Overvolted Vcore|
|AMD Phenom II X4 940 (3.0GHz - 1.32V)||3.2GHz||3.9GHz||30%||1.52V|
|AMD Phenom 9950 BE (2.6GHz - 1.26V)||3.03GHz||3.38GHz||30%||1.45V|
|Intel Core i7-920 (2.66GHz - 1.32V)||3.83GHz||4.0GHz||50%||1.35V|
|Intel Core 2 Quad Q9550 (2.86GHz - 1.22V)||3.48GHz||3.91GHz||38%||1.35V|
We disabled the power management features and manually set the voltages to stock values. Leaving the BIOS settings at Auto will generally result in the BIOS auto-leveling voltages to handle the increased clock speeds for the processor, memory, and bus speeds. We did not get very far with our particular 940 sample as it only reached 3.2GHz resulting in a dismal 7% increase in clock speed. With the exception of the PCMark Vantage TV/Movies test suite and our Flight Simulator X benchmark, this 940 processor passed all other tests at 3.45GHz. The Phenom 9950BE had a 17% increase in clock speed while the i7 920 managed a stunning 50% improvement in clock speed. The E0 stepping Q9550 managed a 23% improvement in core speed.
In our second test, we manipulate voltage settings ranging from the normal VCore/VDimm to VTT/IOH/PCIe until we reached the load limits on the retail air-coolers. Higher-end air-coolers improved clock speeds slightly (3~5%) while dropping core temperatures up to 9C in certain cases.
The clocking situation improved greatly with our 940 once VCore rose to a final 1.52V. We actually hit 4GHz but needed 1.58V to do it. This resulted in a few crashes due to temperatures, but we also noticed our particular CPU sample just was not stable at 4GHz+ even with additional voltages and cooling. The results for the two Intel processors are simply superb in this particular test with the 9950BE managing a respectable 30% improvement in clock speeds, matching that of the Phemom II percentage wise.