Skip to main content

AMD Unleashed: Four CPUs, Two GPUs, All Overclocked

Overclocking

In order to truly squeeze performance from each of these processors, we pushed them hard and were willing to use up to 1.55 V for the Phenom IIs if the Xigmatek cooler could keep load temps from going much above 50 degrees Celsius. Apart from pushing the northbridge frequency, the limits were already widely known for three of the processors.

Image 1 of 2

Image 2 of 2

When it was time to overclock the new Phenom II X3 720 BE, I eagerly started to raise the multiplier, hoping it would even surpass the high marks the Phenom II X4 940 BE set. But when stability testing at 3.4 GHz quickly resulted in a blue screen (suggesting that we had already exceeded the limits at stock voltage) hopes diminished into a hunch that this particular chip was not going to be as stellar an overclocker. 

Image 1 of 2

Image 2 of 2

Along the way, the Phenom II X3 720 BE required a voltage boost one-half multiplier (100 MHz CPU core speed) lower than the Phenom II X4 940 BE. For instance, reaching 3.6 GHz required 1.45 V with this chip versus the 1.40 V required for the previously-tested Phenom II. Final hopes of a higher-than-average overclock were crushed when the chip simply lost stability at 1.525 V and above. 

Image 1 of 2

Image 2 of 2

With a sweet spot of about 1.5 V, the chip initially passed 30 minutes of Prime95 stability testing at 3.7 GHz (18.5 * 200). In the end, we learned that it was not completely stable above 3.67 GHz (18 * 204). From there, the northbridge multiplier was raised to 12 resulting in a northbridge frequency of 2,449 MHz, and the HyperTransport (HT) was set back to its stock multiplier. The DDR2-1066 modules from Corsair did not require additional voltage for this small memory overclock.

Image 1 of 2

Image 2 of 2

In the CPU-Z memory screenshots, you may have noticed we were using unganged mode with each processor. Ganged mode is often the default BIOS setting and is considered to be better for single-threaded applications, while unganged can provide better performance in multi-threaded applications. Some initial testing was performed in both modes, with results indicating that neither really provided a large overall advantage. Unganged mode offered a slight edge in applications and games, while ganged mode took a few wins and provided much higher memory bandwidth scores in the Synthetic Sandra VII benchmark. So, while there may be specific applications for which one mode provides a real advantage over the other, overall, at least in our tests, effects are minimal.

As in our SBM series, the graphics cards were overclocked. We also sought to use the same GPU and GDDR5 frequencies that we used in the last round of $1,250 and $625 SBM PCs. The closest available GPU setting for the Radeon HD 4870 X2 was 782 MHz, which was 2 MHz higher than what Catalyst Control Center (CCC) allowed for the Sapphire Radeon HD 4870 X2. The memory was run at 950 MHz GDDR5, which was identical to the overclocked $1,250 PC’s memory speed.

However, this Radeon HD 4870 had a GPU core limit of 790 MHz in CCC, which was 15 MHz less than the Sapphire Radeon HD 4870’s core limit in the $625 PC SBM. Attempts were made to attain a clock speed of 805 MHz with Riva Tuner, and while the GPU didn’t artifact, the overclocking didn’t seem to stick, and performance occasionally throttled back to stock speeds during testing. In the end, we had to go with CCC, attempting to make up for the lower GPU frequency by running the GDDR5 at 950 MHz versus the 930 MHz with which our Sapphire card topped out.

  • setting aside 1366 and AM3

    In 2 or 3 years when QX9770 chips start showing up for $250-$300.

    Will AMD have a cheaper socket AM2+ compatible chip on the market that will outperform it?

    If so, AMD would be a nice alternative.
    Reply
  • setting aside 1366 and AM3

    In 2 or 3 years when QX9770 chips start showing up for $250-$300.

    Will AMD have a cheaper socket AM2+ compatible chip on the market that will outperform it?

    If so, AMD would be a nice alternative.
    Reply
  • In 2 or 3 years Intel will have 16 cores on a single cpu, and amd tech will, as always, be useless, outdated, and worthless... Just like they are now.
    Reply
  • radguy
    So did I miss somthing or where does it say what each of these processors is overclocked to. I get that the p2 x3 720be is at 3.67 but what about the rest of them. Am I missing it somewhere (very possible) or do I have to look back at your previous articles to figure it out? shouldn't that be on the test systems and configuration page. I am trying to sort through the data.
    Reply
  • dirtmountain
    Nice article Paul and some exhaustive work! Don't overlook the 780G/SB710 that also feature ACC for a price of $72
    http://www.newegg.com/Product/Product.aspx?Item=N82E16813157154
    making the Phenom2 x3 720 a viable option in the SBM budget category. I'm also going to be curious about the new Phenom2 x2 and Athlon2 x2 processors that are coming out June 2nd.
    Reply
  • apache_lives
    Has anyone noticed the benchmarks for the i5's on anandtech yet?
    Reply
  • nerrawg
    Great article guys - love the comparisons to the SBM machines - really gives some insight into CPU and GPU scaling and how much to spend on your processor versus your graphics for gaming builds. Thanks!
    Reply
  • Sihastru
    apache_livesHas anyone noticed the benchmarks for the i5's on anandtech yet?
    I did. Considering the pricing scheme of the i5 (so close to AMD) and it's high performance numbers (so close to the i7) AMD is in big trouble.

    Intel will shift all the processors that are now under the i7 (even if the 920 is rumored to become EOL, one step down on it's portfolio, which means high end Intel dual cores, will go into or under the mainstream, where AMD already has a hard time.

    This doesn't make me very happy, even if I am an Intel fanboy. Aggressive pricing schemes are overrated. AMD needs something new. Now.
    Reply
  • DjEaZy
    ... BIG THX to the Tom's crew... was not so hard after all? ... now, thx to YOU, we have a info about intel, nVidia and AMD/ATi solutions... how they stack up in price/performance/cost of ownership... NICELY DONE!!!
    Reply
  • erdinger
    Yes thanks, many people complained in the system builder marathon and you listened to the complaints... great.
    Reply