Overclocking Specifics

Strange as it might seem, but the first impressions from CPU overclocking on Foxconn A7DA 3.0 mainboard were extremely positive. We used a new AMD Phenom II X4 955 processor and we previously overclocked it on Asus M4A78T-E mainboard in order to find out what it is capable of. The CPU from Black Edition family features an unlocked clock frequency multiplier and we took advantage of this feature to simplify and speed up our overclocking experiments. The system remained stable up until the multiplier hit 19x, i.e. we managed to overclock this processor to 3.8 GHz. Foxconn A7DA 3.0 mainboard could easily repeat the same result.

However, not all processors come with an unlocked multiplier that is why we decided to see how well we could overclock by raising the clock generator frequency. What multiplier should we set for the CPU in this case? AMD Phenom II X4 family includes CPUs from 900 and 905 models that work with 12x and 12.5x multipliers, but this is definitely not the best example, because they belong to energy-efficient type of solutions. There is also a regular, non-energy-efficient AMD Phenom II X4 805, but in the end we decided to go with a 13x multiplier. There are two processors that work with this multiplier at 2.6 GHz frequency: AMD Phenom II X4 810 and 910.

Simple calculations showed that to achieve 3.8 GHz frequency with a 13x multiplier we had to increase the clock generator frequency to 292 MHz. this is when the problems started to surface: Foxconn A7DA 3.0 mainboard refused even to boot at this frequency. The problem was that that board’s WatchDog Timer technology that monitors the successful progress of the POST didn’t work correctly, or was simply missing at all. If the boot-up fails, then normally mainboards would restart in safe mode giving you the opportunity to change the incorrect BIOS settings. Foxconn A7DA 3.0 doesn’t know how to do it. Even if it can restart, then the only way out is to clear CMOS completely. However, the mainboard doesn’t know how to save BIOS settings profiles, so once to resort to this drastic measure you have to reset ALL parameters again, including even date and time!

After a few unsuccessful reboots, we decided to do what we should have done right from the start: find out the maximum clock generator frequency at which the mainboard would remain stable. To eliminate any possible limitations, we lowered the North Bridge and HyperTransport bus frequencies. Soon we managed to find out that with the multiplier lowered to 10x, i.e. at an even lower than the nominal CPU frequency, the board can only boot at 260 MHz clock generator frequency, and at 270 MHz all settings need to be cleared again.

It was obvious that the potential of Foxconn A7DA 3.0 was not enough for us to achieve acceptable overclocking results that is why we went back to overclocking using the clock frequency multiplier. I have to stress that unlike Intel processors, AMD CPUs keep all their power-saving technologies up and running even if the processor core voltage increases or multiplier changes to anything other than the nominal. AMD Cool’n’Quiet technology keeps running and lowering the processor core voltage and multiplier in idle mode. However, we learned that it only keeps going on until the multiplier is no higher than 18.5x. In our case we had to push the multiplier to 19x in order to overclock the CPU to its maximum. It is possible even on Foxconn A7DA 3.0, but in this case AMD Cool’n’Quiet won’t work anymore and the CPU will consume much more power than it actually needs. To be fair I have to say that it is not Foxconn’s fault: we saw exactly the same thing on Asus M4A78T-E.

In fact, this problem seemed to be easy to avoid. In order to overclock the CPU to the desired 3.8 GHz frequency, but maintain proper functioning of the processor power-saving technologies, we simply had to increase the clock generator frequency to 206 MHz and set the multiplier at 18.5x. I was sure that Foxconn A7DA 3.0 could handle this overclocking. Ok, done deal, but for some reason the system booted at 205 MHz.

This is how we suddenly revealed another issue with Foxconn A7DA 3.0. It turned out that the board increased the frequency not with 1 MHz increment, but with 2.5 MHz increment, at least in the interval from 205 to 210 MHz. Up until the BIOS setting of 207 MHz the board kept working at 205 MHz, and starting with 208 MHz setting suddenly jumped over to 207.5 MHz. But in this case the resulting CPU frequency with 18.5x multiplier would get close to 3.84 GHz, which was way too high for our CPU sample, so we had to stop at 205 MHz clock generator frequency. What a disappointment…

However, AMD Cool’n’Quiet power-saving technology in this case worked perfectly fine lowering the processor core voltage and frequency multiplier in idle mode.

As you understand, we were somewhat disappointed with the results of our overclocking experiments with Foxconn A7DA 3.0. The success of the mission was relative and only possible due to a Black Edition processor with an unlocked clock frequency multiplier that we had at our disposal, and not to the outstanding abilities of Foxconn A7DA 3.0 mainboard. Summing up, I have to conclude that there are quite a few drawbacks that we uncovered during this test session:

• Too big increment for frequencies and voltages;
• Non-operational WatchDog Timer technology;
• Clearing CMOS resets all BIOS parameters including date and time;
• No options for saving BIOS settings profiles;
• The need to manually calculate all frequencies after changing the clock generator frequency;
• Inability to work at frequencies above 260 MHz clock generator.