OCZ VX Revisited: DDR Updates on DFI nForce4

Performance Test Configuration

All four memories were tested on the DFI LANParty nF4 SLI-DR. The new DFI nForce4 SLI and Ultra are the only current production boards that support the voltages required for top VX performance. An OCZ DDR Booster can be used with motherboards without support for high memory voltages. nForce4 is PCI Express, so we used the PCIe version of our standard nVidia 6800 Ultra for testing. Other components remain the same as used in the memory setup in Athlon 64 Memory: Rewriting the Rules.

The A64 test bed includes components that have been proven in Socket 939 Athlon 64 benchmarking, such as the Socket 939 4000+ (same specifications as FX53), the OCZ Power Stream 520 Power Supply, and the nVidia 6800 Ultra. We have found the 6800 Ultra to be a particularly good performance match to nVidia motherboards.

All other basic test conditions attempted to mirror those used in our earlier Intel memory reviews. However, test results are not directly comparable to tests performed on the Intel test bed.

AMD nForce4 Performance Test Configuration
Processor(s):	AMD 4000+ (FX53) Athlon 64 (2.4GHz, Socket 939, 1 MB cache, Dual Channel, 1000HT)
RAM:	OCZ EL PC4000 VX Gold (DS) 2X512MB Corsair TwinX1024-4400C25 (DS) 2X512MB Crucial Ballistix (DS) 2X512MB OCZ PC3200 Platinum Rev 2 (DS) 2X512MB
Hard Drives	Seagate 120GB SATA 7200RPM 8MB Cache
PCI/AGP Speed	Fixed at 33/66
Bus Master Drivers:	nVidia nForce Platform Driver 6.39
Video Card(s):	nVidia 6800 Ultra 256MB PCIe, 256MB aperture, 1024x768x32
Video Drivers:	nVidia Forceware 71.84 Release
Power Supply:	OCZ Power Stream 520W
Operating System(s):	Windows XP Professional SP1
Motherboards:	DFI LANParty nF4 SLI-DR
BIOS:	N4D310p Release (3/10/2005)

With nForce3 motherboards, we achieved the fastest performance on AMD Athlon 64 chipsets (nForce3, VIA K8T800 PRO) at a Cycle Time or tRAS of 10. However, as we saw in the recent nForce4 SLI roundup, the nForce4 appears to behave a bit differently with memory. In the SLI roundup, we found a tRAS of 7 to be ideal for memory based on Samsung TCCD chips. Therefore, we ran a complete set of Memtest86 benchmarks with only tRAS varied to determine the best tRAS setting for OCZ VX.

Memtest86 Bandwidth DFI nForce4, Athlon 64 4000+, OCZ VX
2 tRAS	2572
3 tRAS	2572
4 tRAS	2572
5 tRAS	2640
6 tRAS	2640
7 tRAS	2640
8 tRAS	2505
9 tRAS	2505
10 tRAS	2505
11 tRAS	2441
12 tRAS	2383

These tests are particularly easy to do with the DFI nF4 boards, since memtest86 is built-in to the BIOS. To boot memtest86, you only have to enable it in BIOS and the system will boot directly into memtest86. This makes it very easy to test various memory timings, but memtest86 should be disabled in BIOS when you are ready to boot into the system.

Memtest86 Bandwidth DFI nF4, Athlon 64 4000+, OCZ 3200 Platinum Rev. 2
4 tRAS	2191
5 tRAS	2191
6 tRAS	2242
7 tRAS	2191
8 tRAS	2191
9 tRAS	2141
10 tRAS	2092

Similar tests were also run on Crucial Ballistix, Corsair PC4400, and OCZ Platinum Rev.2. All 3 memories showed their best bandwidth at a tRAS setting of 6 - just like OCZ VX. Therefore, a tRAS setting of 6 was used for testing wherever possible.

Test Settings

All AMD Athlon 64 processors are unlocked downward, and the FX CPUs are unlocked up and down. This feature allows a different approach to memory testing, which truly measures performance differences in memory speed alone. All tests were run with CPU speed as close to the specified 2.4GHz of the 4000+/FX53 as possible, with CPU speed/Memory Speed increased at lower multipliers to achieve 2.4Ghz. This approach allows the true measurement of the impact of higher memory speed and timings on performance, since CPU speed is fixed, removing CPU speed as a factor in memory performance.

The following settings were tested with the OCZ EL PC4000 VX Gold on the DFI nF4 test bed:

1. 12x200/DDR400 - the highest stock memory speed supported on K8T800-Pro/nF3-4/SiS755-FX motherboards
2. 11x218/DDR436 - a ratio near the standard DDR433 speed
3. 10x240/DDR480 - a ratio near the standard rating of DDR466
4. 9x267/DDR533 - a standard memory speed used in testing other high-speed memory
5. Highest Memory Performance - the highest memory bandwidth and game performance that we could achieve with the memory being tested. This is rarely the highest memory speed that we could achieve; it is normally a lower speed with 1T Command Rate and tighter memory timings.

Command Rate is not normally a factor in Intel 478 tests, but it is a major concern in Athlon 64 performance. A Command Rate of 1T is considerably faster on Athlon 64 than a 2T Command Rate. For this reason, we had added the Command Rate to the timings and voltage reported for each memory speed setting.

We ran our standard suite of memory performance benchmarks - Quake 3, Return to Castle Wolfenstein-Enemy Territory-Radar, Super Pi 2M, and Sandra 2004 Standard and UnBuffered.