Intel’s transition of the Pentium 4 processor family to the 800MHz system bus was an important event not for the CPU market only, but for the memory market as well. Pentium 4 CPUs with 800MHz FSB required new chipsets.
We have them now – the i875 and i865 chipset families, which also allow using dual-channel DDR400 SDRAM for the memory subsystem. Moreover, the use of DDR400 SDRAM with these processors is not only possible, but even necessary to reach the highest performance. It’s not only because DDR400 SDRAM and the 800MHz bus can work synchronously, thus eliminating the latencies that occur otherwise.
The main advantage of this combination is that the bandwidths of the memory and system buses match each other. The 64-bit Quad Pumped Bus of the modern Pentium 4 CPU working at 800MHz provides a bandwidth of 6.4GB/s. This is the exact match of the bandwidth of two DDR400 SDRAM channels. This is the main reason for us (and for Intel) to say that the dual-channel DDR400 if the optimal memory subsystem for the top-end Pentium 4 processor today.
It should also be mentioned that Intel spends much effort to promote the 800MHz bus into the masses. Intel’s plans for the next year don’t contain Pentium 4 models with a slower bus. The Quad Pumped Bus with 400 and 533MHz frequency will only remain within the value Celeron processor family.
Thus, the DDR400 dual-channel chipsets have been given the green light. Until the arrival of DDR II memory, scheduled for the middle of 2004, these chipsets will remain the top-end solution for the high-performance Pentium 4 platform.
Of course, DDR400 memory modules have caught the spotlight and now enjoy pretty high demand. Memory makers reacted to it by constantly increasing the supply. However, DDR400 modules currently in the market differ greatly in their characteristics. With this article we will try to share our recommendations on the approach to making the right choice about the PC memory. We will not dwell on particular modules for long, but will rather focus on general problems. The questions we are going to answer include:
- How do memory timings influence the overall performance of the Pentium 4 platform?
- Is it profitable to use high-speed overclocker memory when speeding up a Pentium 4 processor?
- What is more important for the Pentium 4 platform – higher memory frequency or lower latency?
- Are there any “ideal” memory modules?
Some time ago, we have carried out a similar investigation for the Athlon XP platform (see our article called DDR400 SDRAM with Athlon XP Platform: Performance and Future Potential). This time it is Pentium 4’s turn.