Foxconn and Gigabyte Tackle Socket AM2

Overclocking

As is typical of Gigabyte motherboards, you have to press Control+F1 in order to reveal many advanced options within the BIOS. We don't particularly like this mechanism, and would prefer that Gigabyte simply embed any settings that they feel are dangerous under additional submenus. Still, as long as you know how to access the advanced functions, it's not a major problem. The major area that you can access to by pressing Control+F1 is the advanced chipset menu, where the most important items are memory timings and HyperTransport multipliers. It's a bit odd that voltage adjustments and bus speeds can be accessed in the overclocking submenu, as tweaking the memory settings usually plays a critical role in achieving maximum performance and stability out of an overclock. That said, let's see how the system does in our stress testing.

Gigabyte GA-M59SLI-S5
Processor:	AMD Athlon 64 X2 - 4800+ (AM2)
Chipset:	nForce 590SLI
CPU Voltage:	1.55V (1.300V default)
Memory Settings:	5-5-5-18 2T 12x Multiplier 4-4-4-12 2T 9x Multiplier
DDR2 Results:	12 x 256HTT = DDR2 1025 9 x 307HTT = DDR2 790
HT Multiplier:	5x below 300HTT, 4x above 300HTT
Memory Voltage:	2.2V
Chipset Voltage:	1.6V
HT Voltage:	1.35V
Cooling:	Zalman CNPS9500 AM2
Power Supply:	OCZ GamexStream 700W
Maximum CPU OverClock:	256HTT x 12 (3075MHz) +28%
Maximum FSB OverClock:	307HTT x 9 (2764MHz) +53%

We initially ran into a severe difficulty with the Gigabyte board and their original BIOS. All attempts to adjust the CPU multiplier had no affect once we were running Windows. This limited the amount of overclocking testing we could perform, but we were eventually able to track down the cause of the problem to a conflict with the AMD Cool-n-Quiet driver. The early BIOS versions we've tested lack the ability to disable AMD's Cool-n-Quiet feature, so once Windows is loaded the driver takes over and any BIOS CPU multiplier settings are lost. Certain applications (like PCMark05) require the driver in order to generate correct results, so hopefully Gigabyte will have a final fix for this issue by the time this board becomes available for purchase.

Once we figured out the problem and hacked the AMD driver, we were able to reach a maximum CPU overclock of 12 x 256 MHz resulting in a CPU speed of 3072 MHz. This was done using the same 4800+ CPU as the previous AM2 motherboard article, and almost matches the results of the Biostar board. Once we switched to a lower CPU multiplier, we were able to run at a maximum HTT bus speed of 308 MHz. This is slightly lower than other premium AM2 motherboards we have tested, and it could easily be explained by the early nature of our particular board. We should be getting a final retail sample in the near future, so we will update our maximum HTT results at that point in time. In the meantime, a 308 MHz HTT bus should still be enough to get the most out of nearly any dual core AM2 processor, unless we start seeing X2 chips that only come with a 9X multiplier.

Memory Stress Testing

The Gigabyte board does not offer the fine granularity of memory voltage controls that the Foxconn board provides, as you are only able to increase voltage in 0.1V increments. We would prefer at the very least 0.05 V increments, and even better are the 0.025V increments that Foxconn and others offer. However, the end result of our memory stress testing with the Gigabyte board turned out to be extremely positive.

Gigabyte GA-M59SLI-S5 Stable DDR2-800 Timings - 2 DIMMs (2/4 slots populated - 1 Dual-Channel Bank)
Clock Speed:	200MHz
Timing Mode:	800MHz - Default
CAS Latency:	3
RAS to CAS Delay:	3
RAS Precharge:	3
RAS Cycle Time:	8
Command Rate:	1T
Voltage:	2.2V

With two DIMMs installed, testing was completely stable at 3-3-3-8 2T timings at DDR2-800. (Note that in actual practice we have determined a tRAS setting of 13 to be slightly better overall in performance with our memory modules.) After further tuning, we were also able to run 3-3-3-8 1T timings at DDR2-800, with the Bank Cycle Time (tRC) set to 18. That makes the Gigabyte board the first AM2 motherboard in our labs to successfully run with a 1T command rate at DDR2-800. This results in slightly faster performance, though as with many memory tweaks the difference between 1T and 2T is not something you would typically notice without running benchmarks -- it's on the order of maybe 1-2% faster.

Gigabyte GA-M59SLI-S5 Stable DDR2-800 Timings - 4 DIMMs (4/4 slots populated - 2 Dual-Channel Banks)
Clock Speed:	200MHz
Timing Mode:	800MHz - Default
CAS Latency:	3
RAS to CAS Delay:	4
RAS Precharge:	3
RAS Cycle Time:	9
Command Rate:	2T
Voltage:	2.2V

Installing four DIMMs stresses the memory subsystem further, and it should come as little surprise that we had to drop the command rate back to 2T. We were able to continue to run with 3-4-3-9 2T timings, however, once again matching what the best socket AM2 motherboards are able to achieve at DDR2-800 with our Corsair PC2-8500 DIMMs.