We carried out our tests on a testbed that included the following components:
- Asus M5A99X EVO rev.1.01 (Socket AM3+, AMD 990X/SB950, BIOS version 0810);
- Asus M5A97 EVO rev.1.01 (Socket AM3+, AMD 970/SB950, BIOS version 0810);
- AMD FX-8150 CPU (3.6 GHz, Zambezi (Bulldozer), AM3+);
- 2 x 2048 MB DDR3 SDRAM Patriot Extreme Performance Viper II Sector 5 Series PC3-16000, PVV34G2000LLKB (2000 MHz, 8-8-8-24 timings, 1.65 V voltage);
- MSI N570GTX-M2D12D5/OC graphics card (Nvidia GeForce GTX 570, GF110, 40 nm, 786/4200 MHz, 320-bit GDDR5 1280 MB);
- Kingston SSD Now V+ Series (SNVP325-S2, 128 GB);
- Scythe Mugen 2 Revision B (SCMG-2100) CPU cooler and an additional 80x80 mm fan for cooling of the area around the CPU socket during overclocking experiments;
- ARCTIC MX-2 thermal interface;
- CoolerMaster RealPower M850 PSU (RS-850-ESBA);
- Open testbed built using Antec Skeleton system case.
We used Microsoft Windows 7 Ultimate SP1 64 bit (Microsoft Windows, Version 6.1, Build 7601: Service Pack 1) operating system, Nvidia GeForce Driver 280.26 graphics card driver.
Operational and Overclocking Specifics
We had no problems building our test configurations with the M5A99X EVO and M5A97 EVO except that we got samples with older BIOS versions which did not support the Socket AM3+ Bulldozer series. So, we had to first install an old Socket AM3 processor to update the firmware and then the mainboards could start up with the new AMD FX-8150. Both mainboards worked with the new CPU correctly, enabling Turbo and power-saving technologies. The frequency and timings of the memory modules were set up at 1067 MHz and 7-7-7-20-1T, just as written in their SPD. However, if the EPU Power Saving Mode (an exclusive power-saving technology of ASUS mainboards) was enabled, the timings were increased to 9-9-9-24-1T. Moreover, they remained too high even after we disabled that technology. We could only bring the timings back to their defaults by loading the optimal BIOS settings or a profile where the EPU Power Saving Mode option hadn’t been changed.
This problem was observed with both mainboards, so we suspect it to be present with the rest of ASUS’s new Socket AM3+ products, too. By the way, the ASUS Crosshair V Formula defaults to memory timings of 9-9-9-24-1T, too, and we benchmarked it at such settings, which affected its performance in certain applications. It turns out that the mainboard may have selected correct timings at first, but spoiled them after our enabling EPU Power Saving Mode. The latter can be turned off not only in the mainboard’s BIOS but also with the hardware EPU switch. The timings will be normal then until you change anything in BIOS settings. Hopefully, the manufacturer will do something about this problem to make its mainboards both fast and energy-efficient without making the user choose between the two.
As for overclocking, the M5A99X EVO could easily clock our CPU at its highest frequency of 4.5 GHz. We only had to increase the CPU voltage higher than usual. The memory modules worked correctly at 1867 MHz. The mainboard has a slightly overclocked base frequency, so the effective CPU and memory clock rates are somewhat higher than the mentioned numbers.
We had had no problems overclocking our AMD FX-8150 to 4.5 GHz with every ASUS mainboard, but the M5A97 EVO was the first exception. We couldn’t make it stable even at a CPU clock rate of 4.4 GHz. MSI’s 990FXA-GD80 hadn’t been able to clock our CPU at 4.5 or 4.4 GHz, either, so we tried to change the frequency multiplier in case these mainboards didn’t like the one we used. We increased the base clock rate to 204 MHz and set the multiplier at x21.5, yet the M5A97 EVO wasn’t stable anyway. We tried to turn various power-related technologies on and off but had to eventually limit ourselves to 4.3 GHz. The good news is that we could increase the North Bridge clock rate to 2400 MHz and the memory frequency to 1867 MHz.
Overclocking often serves as a means of raising one’s self-esteem or demonstration of one’s abilities and skills. However, overclocking for the sake of overclocking doesn’t have much practical value. In our opinion, if you are willing to accept certain risks connected with overclocking, it should reward you by higher performance, or shorter computational time. Overclocking may deliver some quality improvements, allowing one to play games at higher screen resolution or with higher image quality settings. However, at the same time the overclocked system should remain stable and comfortable to work with. It makes no sense to waste a ton of energy by making your CPU ran at high speed and voltage, when it is totally uncalled for. Therefore, when we overclock our systems, we make sure that it could be used permanently in such mode. For the same reason we do not disable any features, e.g. onboard controllers, and try to keep the CPU's power-saving features up and running. The ASUS mainboards were overclocked in this manner, too. When idle, they lowered the CPU's voltage and frequency multiplier to save power.