Overclocking and Conclusion

I have not been able to do an in-depth discovery of new features in AM3 overclocking, but I was able to take a few minutes and see where the X4 955 was able to go.

On the AM2+ platform with a mature BIOS, I was able to reach 3.7 GHz stable with stock voltage.  I was able to do 3.8 GHz with 1.45, but it was flaky at best.  I chose not to push it any farther, as it seems like I hit a wall at 3.8, and one of the cores just didn’t like it.  Again, 3.7 GHz was stable at stock voltage, so it is a pleasant surprise for anyone buying this part.

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AMD is now including a somewhat new heatsink/fan combination in their PIB packages.  This particular number will be included with the X4 955 boxes.

I was able to take the uncore portion to 2.4 GHz with voltage sitting at 1.45v as well.  Running at 3.6 GHz core and 2.4 GHz uncore led to some nice performance increases over stock.  I was hitting 15 GB/sec in memory bandwidth, and the 955 at that speed was acting more like a Q9650 and Q9750 (depending on the application).  AMD could really improve the overall effectiveness of the processor if they were willing to go above 2.0 GHz on the uncore portion, as it affects not only the memory controller, but also perhaps more importantly the L3 cache.  I believe the reason why AMD does not clock up the uncore portion above what they do is mainly due to power.  Caches are typically the most power hungry portions of a processor as they are “on” all the time, as compared to portions of the core which may not be doing any work.  Plus caches are so dense, they utilize more transistors per square mm than other portions of the design.  You put those together, and we see that they can suck up a lot of power.

Individual mileage will vary, but I found that the 955 was a tad more stable on the AM2+ platform than the AM3 board.  This could be due to the BIOS maturity that we see between the older board and the new.


Make no mistake, AMD has another solid part on their hands.  The Phenom II X4 955 performs up to expectations, it does not consume all that much more power than previous versions, and the updates to the clockspeeds and DDR-3 memory make it a much more interesting part.  Now that we actually have a larger selection of AM3 motherboards from $109 to $199, consumers have some very good choices in where they want to put their money.  I certainly do not think that the X4 955 is a bad buy, and when combined with the right motherboard it gives comparable performance to an Intel product which can cost anywhere from $50 to $100 more.

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The base and heatpipes are copper, as they conduct heat far more efficiently than a pure aluminum design.  Aluminum on the other hand is superior to copper in dissapating heat into air.

Global Foundrie’s 45 nm process is really hitting its stride, and I expect to see further improvements in power consumption and clocking ability of products based on this process as time moves on.  The original X4 940 is a 125 watt part, but it is clocked 200 MHz lower in core and uncore areas, so it is impressive that AMD was able to improve their product without causing a large spike in overall power consumption.

AMD continues to move forward with new product launches, and it is nice to see that they have now fully fleshed out their AM3 offerings.  The two new processors dropped on the market today will allow users to have a greater selection of products to choose from.  With better cooling I likely would have been able to hit 4 GHz, and certainly the 3.8 GHz I was able to achieve is outstanding compared to how little work I had to do to get there.

While the Phenom II processors are not entirely competitive with the i7 cores, AMD has certainly been executing at a very high level as of late.  Considering that the Phenom II is actually a larger chip in terms of die size and transistor count than the i7, we catch a glimpse of how really impressive the i7 is.  For the time being AMD is not attempting to directly compete with the i7, but rather with the still powerful Core 2 Quad series.  Add in the fact that the Phenom IIs do overclock to high speeds, and have enough features to keep most enthusiasts happy, we must not forget that they are just plain fast processors.

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The combination of copper + aluminum in such a configuration allows for good cooling of this high end part.  While it is not superior to larger solutions, it is able to keep a stock clocked Phenom II X4 955 around 45 degrees C at full load.  Overclocking with this cooler is possible, but will not produce outstanding results.

The X4 955 is a significant development for AMD as they are finally expanding into the AM3 platform and embracing DDR-3 as a high performance addition to their arsenal.  Hopefully in the next few months we can catch a glimpse of what new and interesting things AMD will offer on the desktop.

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