We found some differences between our AMD 890GX-based mainboards when we checked out their overclocking potential. On the AMD 785G-based Gigabyte MA785GT-UD3H mainboard we compare the new mainboards with, our Athlon II X4 635 processor was found to be stable at a peak frequency of 3625 MHz. To achieve that frequency the CPU voltage was increased by 0.1 volts to 1.5 volts and the clock generator's frequency was lifted up from the default 200 to 250 MHz. The memory frequency was increased to 1666 MHz at that, which provoked no problems. The frequency multipliers for the integrated North Bridge and the HyperTransport bus were manually lowered from 10x to 8x so that the resulting frequencies were as close to the default ones as possible.
Running a little ahead, we can say that both AMD 890GX-based mainboards easily coped with such overclocking. Moreover, they both improved that result somewhat, to our satisfaction.
To be specific, the ASUS M4A89GTD PRO/USB3 could keep the Athlon II X4 635 stable at a clock generator's frequency of 253 MHz. It means that the CPU frequency was as high as 3668 MHz.
The CPU voltage was set at 1.5 volts and we used 8x multipliers for the frequencies of the HyperTransport bus and integrated North Bridge. The memory frequency grew up to 1686 MHz then.
The Gigabyte 890GPA-UD3H did not get as high as its opponent. At a clock generator frequency of 253 MHz, the mainboard did not pass our stability test. The system was stable at 251 MHz, i.e. at a CPU frequency of 3640 MHz.
The rest of the voltages and frequency multipliers were set at the same values as with the other two mainboards.
Thus, it is with the ASUS M4A89GTD PRO/USB3 that we reached the highest CPU frequency in our overclocking experiments. As for the overclocking potential of the AMD 890GX chipset in general, our tests suggest that it is no worse than that of the AMD 785G. We see no reason why the new chipset cannot be recommended to enthusiasts.
The performance delivered by the overclocked mainboards can be seen in the next diagrams.
The higher CPU frequency achieved with the ASUS M4A89GTD PRO/USB3 makes it the fastest platform in the performance tests. On the other hand, its advantage over the Gigabyte mainboard based on the same chipset is not too large. The difference is a mere 1-2%.
The power consumption of these mainboards is quite a different story. Although the three tested mainboards allow to overclock the CPU without turning off Cool'n'Quiet technology, they behave differently at the increased CPU frequency and voltage.
The ASUS M4A89GTD PRO/USB3 is still highly economical when idle. But when under high CPU load, the power consumption of the system with this mainboard grows up greatly and outruns that of the systems with the Gigabyte mainboards. This must be due to the ASUS mainboard's enabling its Load-Line Calibration feature which increases the voltages a little under high CPU load. Gigabyte's mainboards do not have such a technology and consume less power as the consequence.