by John Reynolds
Introduction
SimHQ’s recent look at AMD’s new AM2 socket saw the introduction of support for DDR2 memory for the company’s Athlon 64 AM2 lineup. Continuing the design of embedded memory controllers, AMD’s new family of dual-core processors work with DIMM speeds up to PC6400 (DDR2/800). Yet DDR2 has lagged considerably behind DDR in memory timings, with Cas4 being the lowest production latency available for DDR2/800. With the announcement of Corsair’s TWIN2x1024-6400C3, the company has introduced the first 800MHz (PC6400) speed grade capable of running with a latency of C3. Today’s article will examine what overall performance impact an AM2 CPU may see with lower latency memory installed in SimHQ’s benchmark suite.
Corsair has partnered with NVIDIA in a collaborative effort to support Enhanced Performance Profiles (EPP). System memory ships with a serial presence detect (SPD) ROM that holds information regarding the memory timings of the modules present, allowing the system to communicate with the SPD so that those timings can be correctly set. Yet a portion of the ROM has traditionally been reserved for manufacturer information, and the partnered companies have proposed an open standard under which that unused area of the ROM can store additional values not generally required by standard SPD specifications. As its title suggests, EPP information stored in the ROM would include detailed values dealing with command rates, latency, and memory voltages for enhancing performance. Home tweakers and overclockers have themselves often achieved higher performance from installed DIMMs, yet this was only through a hit ‘n miss process of tweaking various settings. With an EPP compatible motherboard, home users can choose between two profiles for Corsair’s XMS2 DDR2 line of memory, one for high frequency and the other for low latency.
The ASUS M2N32-SLI Deluxe motherboard, based on NVIDIA’s new nForce 590 SLI chipset, lists these options as SLI-Ready Memory under the CPU Configuration section in the BIOS’ Advanced menu. These BIOS options allow the end user to quickly and easily overclock their EPP DIMMs. Home users could think of it as saying goodbye to the former trial and error process of pushing their system memory beyond its rated specifications. However, the SLI-Ready Memory options, once enabled, must be used in combination with ASUS’ AI Tuning options, also found in the BIOS, a requirement that isn’t exactly well documented for the motherboard.
Last, as stated in the AM2 article, AMD-based systems employ a 200MHz reference clock that acts as the source signal driving all installed components on the motherboard. Thus there is no traditional front-side bus. And all Athlon 64s have a frequency that is derived by multiplying that reference signal with a whole number, which explains the 200MHz incremental clock speed increases of A64 processors. SimHQ’s AM2 article also explained how certain processors, such as the Athlon 64 X2 5000+, actually results in DDR2/800 memory running at 371MHz rather than its full speed grade of 400MHz. This information could be useful to those considering upgrading to an AM2-based system, and is why the AM2 FX-62 is used for testing in this article.
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