ASUS M2N32-SLI & Epox MF570SLI: AM2 Wunderkinder

Overclocking

ASUS M2N32-SLI Deluxe Overclocking Testbed
Processor:	AM2 4800+ (X2, 2.4GHz, 1MB Cache per core)
CPU Voltage:	1.525V (default 1.4V)
Cooling:	AMD Stock Heatpipe FX62 Cooler
Power Supply:	OCZ Power Stream 520W
Memory:	Corsair Twin2x2048-PC2-8500C5 (2x1GB) (Micron Memory Chips)
Hard Drive	Hitachi 250GB 7200RPM SATA2 16MB Cache
Maximum OC: (Standard Ratio)	260x12 (5x HT, 3-3-3-Auto) 3120MHz (+30%)
Maximum FSB: (Lower Ratio)	350 x 9 (4x HT, 3-3-3-Auto) (3042MHz, 2 DIMMs in DC mode) (+75% Bus Overclock)

ASUS told us in meetings that the M2N32-SLI Deluxe was capable of overclocking to a 350 CPU clock speed. At 1.525V on the CPU we reached a highest stable speed of 350x9. This is a 75% bus overclock and the highest speed we have ever reached in any of the AM2 motherboard tests. The M2N32-SLI Deluxe was extremely stable at this speed, and we may have reached even higher speeds if we had dropped the multiplier further, increased the voltage more, or used better CPU cooling. We stayed at the 9x multiplier for consistency with other test results.

At the stock 12x multiplier the system reached 260x12, 3.12GHz, at the same voltage. This is again the highest this CPU has achieved. The ASUS 8-phase design appears to work very well in maximizing stability in overclocking. The passive cooling system was also very effective even at these high overclocks. Again, you may be able to achieve even better results with some active cooling on the chipsets. The SPP, in particular, seems to get hotter than the new 590 MCP and it may benefit from active cooling.

It was very satisfying to reach a stable 350 MHz with a system with passive cooling. The only active fan on the board was the CPU cooler fan, and even that was a stock AMD cooling fan with a heatpipe.

Memory Testing
Optimum tRAS

DDR2 memory behaves quite differently in ASUS tRAS testing than we have seen on other AM2 boards. As you can see from the standard chart below, a 2GB kit of Corsair 8500 (DDR2-1066) experienced the SAME bandwidth no matter what tRAS setting was used. ASUS is apparently controlling and optimizing tRAS timings internally.

Memtest86 Bandwidth ASUS M2N32-SLI Deluxe with AM2 4800+
6 tRAS	3138
7 tRAS	3138
8 tRAS	3138
9 tRAS	3138
10 tRAS	3138
11 tRAS	3138
12 tRAS	3138
13 tRAS	3138
14 tRAS	3138
15 tRAS	3138
16 tRAS	3138
17 tRAS	3138
18 tRAS	3138
AUTO (CPUZ tRAS 18 Reported)	3248

To further test this idea, we also ran tRAS at the AUTO setting, which yielded the highest memory bandwidth in the tRAS tests. To determine the tRAS that was being set by AUTO we looked at memory timings with CPUZ. That utility reported tRAS of 18, which is the highest available setting. We do not really know whether 19 is being set by auto or whether AUTO merely reports the highest setting but then dynamically adjusts tRAS.

Whatever the mechanism, a tRAS setting of AUTO produced the highest memory bandwidth. All stock benchmarking was performed with Corsair 8500 settings of DDR2-800 at 3-3-3-Auto settings at 2.225V.

Memory Stress Testing

The wide range of voltage controls on the ASUS M2N32-SLI Deluxe help users to get the most out of overclocking and the best performance from memory modules. Most DDR2-800 memory is rated at conservative 5-5-5-15 timings, but that's also assuming you only run with the default 1.8 V. We have found in our DDR2 testing that many modules are easily able to run 4-4-4-12 timings at 2.0 V, and the Corsair modules we are testing with (rated at 5-5-5-18 DDR2-1066) are generally able to run with 3-3-3-9 timings with approximately 2.2 V.

ASUS M2N32-SLI Deluxe 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:	Auto (18 Reported)
Command Rate:	1T
Voltage:	2.225V

With two DIMMs installed, testing was completely stable at 3-3-3-Auto 1T timings at DDR2-800. This is very rare for two reasons. First, AMD does not really support 1T timings with DDR2-800 in the current on-chip memory controller, and Gigabyte is the only other board we have tested that can also operate at 1T timings. All of our utilities report operation is at 1T also.

Several benchmarks were run to compare performance at 1T and 2T timings, but we could not find any real-world performance improvements with the 1T timings compared to 2T. AMD is said to be readying a revision to the AM2 memory controller that will officially support 1T Command Rate. Perhaps that new design with support for 1T will make a more significant improvement in performance.

ASUS M2N32-SLI Deluxe 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:	3
RAS Precharge:	3
RAS Cycle Time:	10
Command Rate:	2T
Voltage:	2.225V

The ASUS M2N32-SLI also exhibited remarkable performance with four 1GB DIMMs. Installing four DIMMs stresses the memory subsystem further, but the ASUS was still stable at the same 3-3-3-Auto timings that worked best with 2 DIMMs. As expected, we did have to drop command rate to 2T but we doubt you can measure that impact on a memory controller designed for 2T operation.

The ASUS is the only AM2 motherboard we have tested so far that was able to run four 1GB DIMMs at 3-3-3 timings. That performance speaks very well for the stability of the ASUS design, since the memory controller in all our motherboard tests is the same initial release AM2 CPU.