The memory subsystem is one of the most important computer subsystems in terms of performance. Memory chips are mounted on special boards, called memory modules (Fig. 12.1), installed in special slots on the motherboard. The operating speed of the RAM subsystem — and, consequently, overall system performance — depends on the RAM settings specified in BIOS Setup.
Usually, the required parameters that determine the operation of RAM modules are set automatically. This typically is accomplished via a special parameter known as DRAM Timing. In the BIOS Setup of most contemporary motherboards, it can have two settings: By SPD (Serial Presence Detect) or Manual.
The By SPD value ensures settings recommended by the RAM manufacturer, hard-encoded into the modules. Note that manufacturers usually try to ensure stable operation of their products in all possible computer configurations. In doing so, they tend to raise the latency value too far. This decreases the speed of the memory subsystem and, consequently, degrades overall system performance.
It is possible to improve the performance of the memory subsystem by switching to Manual and setting optimal parameters for the specific memory module.
The rest of this chapter focuses on an investigation of the performance dependence on various settings of the RAM parameters that influence the operating speed of the memory subsystem. (This information is published with the permission of http://www.3dnews.ru, a Russian-language Web site. The English version of this site can be found at http://www.digital-daily.com.)