- Joined
- Aug 15, 2003
- Location
- Ft. Hood, TX
X-bit Labs has a semi-indepth article on Intel P4-C (800 FSB) performance with memory at various settings of latency. The article, Choosing Optimal Memory to Match Intel Pentium 4 Processor, is split into 2 main parts. The first 7 pages deals with what latencies work best while at stock (200MHz) FSB. The second part, from page 8 on, deals with the effect of latency on overclocking performance.
Basically it reconfirms that low-latency is most important. It also confirms that tRCD (RAS to CAS Delay) and tRP (RAS Precharge) are more important then CL (CAS timings). Many times have I seen people post their "tight" timings, which turn out to be something like 2-4-4-5 or 2-4-3-5. They think that because their CAS is 2.0 then they are running good, when in fact they are running at dangerous settings (tRAS should be CAS + tRCD; never less).
The Influence of Async Overclocking with Low Timings (the main arguement) in Real-World (gaming) settings has results shown on page 13. The highest performance occurs when using Async (5:4) with lowest timings. While not graphed, performance would be optimum with memory that is capable of running 230-240MHz (at 2-2-2-5) running 4:5 with FSB.
You all should read the review, but in case your lazy, here are the conclusions:
Basically it reconfirms that low-latency is most important. It also confirms that tRCD (RAS to CAS Delay) and tRP (RAS Precharge) are more important then CL (CAS timings). Many times have I seen people post their "tight" timings, which turn out to be something like 2-4-4-5 or 2-4-3-5. They think that because their CAS is 2.0 then they are running good, when in fact they are running at dangerous settings (tRAS should be CAS + tRCD; never less).
The Influence of Async Overclocking with Low Timings (the main arguement) in Real-World (gaming) settings has results shown on page 13. The highest performance occurs when using Async (5:4) with lowest timings. While not graphed, performance would be optimum with memory that is capable of running 230-240MHz (at 2-2-2-5) running 4:5 with FSB.
You all should read the review, but in case your lazy, here are the conclusions:
- Memory timings affect the performance of the Pentium 4 platform quite perceptibly. So, if you have spent money on an expensive processor, do not save on memory. Memory modules with less aggressive timings will not allow the processor to work at its best.
- Performance is mostly affected by RAS# to CAS# Delay and RAS# Precharge parameters. These are the settings you should strive to reduce in the first place. As for CAS Latency, the influence of this parameter on the performance is less evident than we usually think.
- It is preferable to use the memory and the CPU buses at the same frequency, that is in synchronous mode. That’s why it makes sense to buy overclocker memory, capable of supporting high frequencies, if you are into overclocking. On the other hand, the performance gain you have when using overclocker memory is rather small compared to the performance of ordinary DDR SDRAM working asynchronously with the FSB.
- You should not be afraid of using diminishing coefficients for the memory frequency. If you compensate with lower timings the effects of the asynchronous mode, you will have just a little performance drop.
- Overclocker memory with operational frequencies much over 400MHz cannot work with aggressive timings at 400MHz. Analogously, DDR400 SDRAM that works at 400MHz with 2-2-2-5 timings is usually non-operational at higher frequencies.