915 Motherboard Roundup: Socket 775 for the Rest of Us

AOpen i915Pa-EFRII: Overclocking and Stress Testing

FSB Overclocking Results

Front Side Bus Overclocking Testbed
Processor:	Pentium 4 Prescott LGA 775 560 ES (2.8GHz-3.6GHz)
CPU Voltage:	1.425V (1.3675V default)
Cooling:	Thermaltake Jungle 502
Power Supply:	OCZ Power Stream 520
Maximum CPU OverClock:	217x18 (3996MHz) +9%
Maximum FSB OC:	217FSB x 14 (+9%)

When the 915/925X boards first appeared, there was a lot of talk about a 10% overclock built into the 915/925X chipset. Manufacturers of boards that cater to enthusiasts, like Abit, Asus and DFI, quickly found ways to get around this design issue, but others did not seem to see this as a big problem. AOpen falls into the latter category here. Whether at stock multiplier or the Speedstep reduced 14X, the AOpen will reach 217 and nothing more.

Most users never overclock, and the AOpen is a great board for them, since it contains all the important performance features that are missing on many other 915 boards in the roundup. However, overclockers should look elsewhere for a 915 board as they will be very frustrated to be limited to a 9% overclock.

Memory Stress Test Results:

The memory stress test measures the ability of the AOpen i915Pa to operate at its officially supported memory frequency (533MHz DDR2), at the best performing memory timings that Crucial/Micron PC2-4300U will support. Memory stress testing was conducted by running DDR2 at 533MHz (stock 3:4 ratio) with 2 DIMM slots operating in Dual-Channel mode.

Stable DDR533 Timings - 2 DIMMs (2/4 DIMMs - 1 Dual-Channel Bank)
Clock Speed:	266MHz
Timing Mode:	3:4 (200:266 - Default)
CAS Latency:	3.0
Bank Interleave:	Auto
RAS to CAS Delay:	3
RAS Precharge:	3
Cycle Time (tRAS):	10*
Command Rate:	N/A

*SPD (Auto) timings for DDR2 are normally 4-4-4-12 at DDR2-533. A tRAS setting of 12 is normal. We ran a series of tests to measure memory bandwidth, and found that the tRAS setting made very little difference in the performance of DDR2. The most effective range of tRAS was 8 to 13 for DDR2 on the 925X chipset, so a tRAS of 10 was chosen for benchmarking.

The AOpen i915Pa was completely stable with 2 DIMMs in Dual-Channel at the DDR2 settings of 3-3-3-10 at 1.8V default voltage. These are much faster settings than the DDR2 SPD and rated timings of 4-4-4-12.

Filling all four available memory slots is more strenuous on the memory subsystem than testing 2 DDR2 modules on a motherboard.

Stable DDR533 Timings - 4 DIMMs (4/4 DIMMs - 2 Dual-Channel Banks)
Clock Speed:	266MHz
Timing Mode:	3:4 (200:266 - Default)
CAS Latency:	4.0
Bank Interleave:	Auto
RAS to CAS Delay:	3
RAS Precharge:	3
Cycle Time (tRAS):	10
Command Rate:	N/A

DDR has a long benchmarking history that makes it easier to figure out where to go with memory timings. We are still in the learning curve with DDR2, and the old DDR patterns just do not work in DDR2. We found that no matter what the rest of the settings, 4 DIMMs with DDR2 generally required CAS 4 for stability. Timings like 3-4-3 or 3-4-4 appeared to work fine, and then we were suddenly facing hard drive corruption. Our advice for now is to use CAS 4 with 4 DIMMs for stability, although 4-3-3 timings did work fine on most of the test boards. If you plan on trying to raise voltage to attempt lower CAS with 4 DIMMs, then please backup your system first.