Asus A8R-MVP: Mainstream Rocket

Overclocking

Asus A8R-MVP Overclocking Testbed
Processor:	Athlon 64 4000+ (2.4GHz, 1MB Cache)
CPU Voltage:	1.45V (default 1.40V)
Cooling:	Thermaltake Silent Boost K8 Heatsink/Fan
Power Supply:	OCZ Power Stream 520W
Memory:	OCZ PC3200* Platinum Rev. 2 (Samsung TCCD Memory Chips) *The current equivalent OCZ memory is OCZ PC4800
Hard Drive:	Seagate 120GB 7200RPM SATA 8MB Cache
Maximum OC: (Standard Ratio)	246x12 (4x HT, 2.5-3-3-7) 2952MHz (+23%)
Maximum FSB: (Lower Ratio)	325 x 9 (3x HT, 2T*, 3-4-3-8) (2925MHz, 2 DIMMs in DC mode) (+62.5% Bus Overclock)

Screen captures on the first page have already announced that the Asus A8R-MVP has set new overclocking records in our testing. We actually found 330 to be stable in memtest86 and booted into Windows at a little more than 330 with memory set to a DDR400 starting point. However, Windows was not completely stable at 330 and required a slight lowering to 325 (DDR650). The 325 setting was completely stable, ran our benchmarks, and ran for more than 2 days on just air cooling.

Our first efforts at overclocking the A8R-MVP ran into a road block at just over 260. We have found some Asus boards in the past that did not like overclocks to be immediately set to high values, so we started again at 250. By going up just 5 to 10FSB at a time, we were able to reach 325. Since we had no idea that we would reach such a high OC on this mainstream board, we have screen captures at every 5MHz from about 270 to 330. Our advice to overclockers on this board is to move the overclock up slowly.

*UPDATE: After further testing we have concluded that the A8R-MVP handles 1T timings only to about 260-265. Above 260-265 you will need 2T timings to reach 325 or so clock frequency. We ran into a wall at 260 and apparently the BIOS reset. The default is 2T and we didn't catch the Command Rate reset. This board uses very aggressive timings, and the 2T memory bandwidth was so fast we did not realize the board was actually running at 2T. This does not change the fact that 325 at 2T is an outstanding overclock, but it is achieved at 2T timings, and not at 1T as originally reported.

Those who don't understand overclocking or who don't want to bother will find extensive automatic overclocking options in the Asus BIOS. This allows you to set an overclock and have the board adjust the related settings. These work well for modest overclocking, but they will not allow the extreme results achieved manually on the Asus A8R-MVP.

Memory Stress Testing

The Asus A8R-MVP easily handles 2-2-2-7-1T timings at stock speed, as do almost any of the current boards for AMD Socket 939 from NVIDIA, SiS, VIA, ATI, and ULi. However, the default setting for Command Rate in the Asus BIOS is 2T, and you need to manually set Command Rate to 1T for best performance with 2 DIMMs in Dual Channel mode. Asus tells us that this was done to accommodate some memory manufacturers that had asked for a default 2T Command Rate for maximum compatibility with their memory. Once set, we had no issues using 1T command Rate with any memory that we tested.

Running four double-sided 512MB or 1GB DIMMs is much more demanding than running two DS DIMMs, and Asus did not have any extra magic here. Like every board that we have tested except the DFI RDX200, we needed to drop the Command Rate to 2T with 4 DS DIMMs. With 4 DIMMs, the A8R-MVP remained stable with the same aggressive 2-2-2-7 timings used for two DS DIMMs.

Stable DDR400 Timings - 4 DIMMs (4/4 DIMMs populated)
Clock Speed:	200MHz
CAS Latency:	2.0
RAS to CAS Delay:	2T
RAS Precharge:	7T*
Precharge Delay:	2T
Command Rate:	2T

*7T was determined by MemTest86 benchmarks to deliver the widest bandwidth with the ATI Rx480/482 chipset. While the board would operate at tRAS of 5T or lower, all benchmarks were run at 7T.