DFI nForce4: SLI and Ultra for Mad Overclockers

Memory Stress Testing

Optimum tRAS

In past reviews, memory bandwidth tests established that a tRAS of 10 was optimal for the nForce3 chipset and a tRAS setting of 11 or 12 was generally best for nForce2. Since this was the first memory stress test of a production nForce4 board, tRAS timings were first tested with memtest86, a free diagnostic program with its own boot OS that will boot from either a floppy disk or optical disk. Bandwidth was measured from tRAS 5 to tRAS 11 to determine the best setting.

The best bandwidth was achieved in the 6 to 8 range with this combination of nForce4 and the 4000+, so a mid-value tRAS of 7 was chosen for all tests.

Memory Stress Tests

Our memory stress test measures the ability of the DFI to operate at its officially supported memory frequency (400MHz DDR), at the lowest memory timings that OCZ PC3200 Platinum Rev. 2 modules will support. All DIMMs used for stress testing were 512MB double-sided (or double-bank) memory. To make sure that memory performed properly in Dual-Channel mode, memory was only tested using either one dual-channel (2 DIMMs) or 2 dual-channels (4 DIMMs).

Using two DIMMs in Dual-Channel 128-bit mode, the memory performed in all benchmarks at the fastest 2-2-2-7 timings, at default 2.6V voltage.

Tests with 4 DS DIMMs on an AMD Athlon 64 system are more demanding, since AMD specifies DDR333 for this combination. However, most AMD Athlon 64 motherboards combined with recent AMD processors (the memory controller is on the AMD CPU) have been able to handle 4 DIMMs at DDR400.

Tests with all four DIMM slots populated on the DFI nForce4 boards required a 2T Command Rate with 4 DS DIMMs in two dual channels. This is the pattern seen on other top-performing Socket 939 boards, but we hoped that higher voltage might allow us to eek out 4 DS DIMM 1T performance. However, additional voltage did not help and DDR400 with 4DS DIMMs still required a 2T Command Rate on the DFI nForce4 boards.