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AMD Phenom II X4 975 & 840 Review



Here at OverclockersClub, we put our hardware through a rigorous testing program. We use a combination of scientific and video benchmarks designed to push and stress the components which, along with our own extensive experience, gives us a good idea how they will perform in everyday computing. I placed the AMD Phenom II X4 975 and Phenom II X4 840 processors up against a slew of other AMD and Intel processors so you get a good idea on where they stand among the other choices out there. All the supporting hardware is run at the same speeds, timings, voltages and latencies to ensure that there are no outside variables that will interfere with the scores.


Testing Setup: AMD AM3


Testing Setup: Intel Core i5/i7 Socket 1156


Testing Setup: Intel Core i7 Socket 1366


Testing Setup: Intel Core i5 Clarksdale Socket 1156


Comparison CPUs:



Overclocked settings:

  • Processor: AMD Phenom II X4 975 @ 4320MHz 211x20.5
  • Processor: AMD Phenom II X4 840 @ 3853MHz 241x16

Overclocking the processors took two different steps for each model. The Phenom II X4 975 has an unlocked multiplier, making it easier to just raise the CPU value while keeping other components (such as memory and the HyperTransport BUS) at their stock speeds thereby helping with stability. To start off with overclocking the X4 975, I raised the multiplier 1x at a time until I was no longer able to keep the system stable. I then backed down 1x and started adjusting the reference clock the same way while also pushing up the CPU voltage. With the X4 975, I was able to achieve a nice stable overclock well above 4GHz, which makes a sub $200 CPU an even better bargain. The final speed for the X4 975 was 4.32GHz. When it came to overclocking the X4 840, which has a locked multiplier, I took the same approach as above, but only with the reference clock and the voltage. I started off by increasing the clock speed 5MHz at a time until I reached a wall and then backed off 1MHz at a time. With the X4 840, I was able to push the reference clock to 240MHz for a final overclocked speed of 3.85GHz, which is a mild overclock, but this is what's expected for a lower-end chip.




Maximum Clock Speeds:

Each CPU has been tested for stability at the clock speeds listed when in an overclocked state. These clock speeds will represent the overclocked scores in the testing.




  • Scientific & Data:
  1. Apophysis
  2. WinRAR
  3. Office 2007 Excel Number Crunch
  4. POV Ray 3.7
  5. Bibble 5
  6. Sandra XII
  7. ScienceMark 2.02
  8. Cinebench 10 & 11.5
  9. HD Tune 3.50
  • Video:
  1. Far Cry 2
  2. Call of Duty: Modern Warfare 2
  3. Batman: Arkham Asylum
  4. 3DMark Vantage

  1. Introduction & Closer Look
  2. Specifications
  3. Testing: Setup & Overclocking
  4. Testing: Apophysis, WinRar, Bibble 5
  5. Testing: Office 2007, POV Ray, Geekbench
  6. Testing: SiSoft Sandra 2010
  7. Testing: Sciencemark, Cinebench, HD Tune
  8. Testing: Far Cry 2
  9. Testing: Call of Duty: Modern Warfare 2
  10. Testing: Batman: Arkham Asylum
  11. Testing: 3DMark Vantage
  12. Conclusion
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