Overclocking the Easy Way

Now that we have described all the features of our today’s platform, it is high time we moved on to the main part of our today’s article. Namely, we are going to discuss our AMD Phenom 9600 Black Edition overclocking experiments performed on DFI LANParty UT 790FX-M2R mainboard. Besides these two irreplaceable components of our today’s testbed, we also used a pair of 1GB Corsair TWIN2X2048-10000C5DF DDR2 SDRAM modules, OCZ GeForce 8800GTX graphics card and Western Digital WD1500AHFD hard disk drive. The CPU was cooled with Zalman 970CNPS LED air cooler.

Since AMD Phenom 9600 Black Edition processor has an unlocked clock frequency multiplier it would make perfect sense to overclock it using this particular advantage.  That is why overclocking CPUs from the Black Edition family hardly ever causes any problems. To get it to run at any frequency above the nominal, all you need to do is change the clock multiplier in the BIOS Setup. You can also increase its core voltage, if you wish.

Without any Vcore adjustments, our AMD Phenom 9600 Black Edition processor worked stably at maximum 2.6GHz obtained with 13x multiplier setting.

In this case, just like in all other experiments, we tested the system stability with 1-hour run of Prime 25.5 utility.

The second batch of experiments was performed with the processor Vcore increased to 1.45V. However, changing only this one parameter didn’t prove as efficient for overclocking results. In fact, by raising only this voltage, we couldn’t get our CPU to surpass the same 2.6GHz frequency achieved before.

As we found out later on, you should also increase the second processor voltage – that of the North Bridge integrated into the CPU – if you want to achieve even better results on AMD Phenom 9600 Black Edition processor. New Socket AM2+ mainboards allow adjusting this voltage setting independently of the main processor Vcore. It is not for nothing that there is the whole dedicated phase responsible for this particular parameter in the processor voltage regulator circuitry. Once we set this parameter at 1.3V, we could increase the CPU frequency to 2.7GHz.

At this speed our processor passed the one-hour Prime stability test, however, later one we discovered that it doesn’t indicate full stability at all. Further performance tests revealed some problems in resource-hungry applications that is why we had to roll back to 2.6GHz speed to make sure that we can pass the full set of benchmarks.

Unfortunately, further voltage increase didn’t improve our overclocking results. Even at 2.6GHz frequency with increased voltages the CPU was heating up a lot. Unfortunately, we cannot share with you the objective thermals, because the temperature readings reported by all diagnostic utilities including AMD OverDrive were too low to be true.

Here we could have ended our discussion on overclocking AMD Phenom 9600 Black Edition processor by raising its clock frequency multiplier, if it hadn’t been for one thing. Unlike their predecessors, Socket AM2+ processors theoretically support much more fractional multipliers. While Socket AM2 processors can only offer multipliers with 0.5x increment, new Phenom CPUs can work with a much broader range of non-integer multipliers.

This way the Phenom multiplier is set not with one but with two parameters called CpuFid and CpuDid in the whitepapers. The resulting multiplier K can be calculated using the following formula:

The BIOS of advanced Socket AM2+ mainboards allows adjusting both these parameters. For example, in case of DFI LANParty UT 790FX-M2R that we used today, these options are available in CPU Feature section.

At the same time, DFI engineers made this formula a little simpler, so that it looks as follows for this particular mainboard:

So, Phenom clock frequency multipliers can theoretically vary with a very tiny increment. This features is also used by Cool’n’Quiet 2.0 technology that can adjust CpuDid parameter when switching to power-saving mode. That is why Phenom processors can sometimes surprise you with their strange multipliers in idle mode.

However, computer enthusiasts have their own plans for this feature of the new AMD processors. In fact, AMD offers them the opportunity to adjust the Phenom 9600 Black Edition processor frequency with very small increment using only frequency multiplier. Although we haven’t yet managed to really use these theoretical assumptions in reality. When we set CpuDid to anything other than 1 on our DFI LANParty UT 790FX-M2R mainboard, the system would hang on boot-up if the CpuFid exceeded 24. In other words, the only fractional clock multipliers obtained with the increment smaller than 0.5x, turned out too small for overclocking needs.