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As always, everything always boils down to money and that's why we have this dilemma; to run faster memory with slower access times, or run slower memory with faster access times.
There are two trains of thought on this,
first is that high speed DIMMs (like PC4000 DDR) can make up for running slower timings by amount of bandwidth provided to processor. Specifically, bandwidth is amount of data that can be moved from one given device to another.
Most DIMMs that run tight timings, such as certain PC3200 & PC3500 modules, have to run memory at lower MHz than FSB. However, when overclocking to extreme speeds these DIMMs are bandwidth limiting processor. What I mean by this, is that when processor requires a great deal of bandwidth, CPU will have to wait for another clock cycle before being filled, as memory is just not fast enough to keep up at same pace. Having a large pool of bandwidth is great when you're working with applications that process a lot of raw data, such as Photoshop or databases for example.
The other point of view is that CAS2-rated PC3200 & 3500 memory can make up for lack of bandwidth because memory has a lower latency that in effect moves data between CPU and memory faster. Programs that do not require a large amount of bandwidth tend to benefit more from quicker data transfers between memory and rest of computer such as games or 3D applications.
2-3% Improvement
While bandwidth is still very important to Intel Pentium 4, it's not as important as it once was in i845PE days of single channel memory controllers. Thanks to i865PE/i875P's dual channel memory controller things are much brighter. On average, system with memory running at 400 MHz (5:4 memory divider enabled) with aggressive memory timings performed 2-3% faster than system using high speed memory with loose timings.
While that may not seem like a lot to most people, it can make a world of a difference to enthusiast, especially if you're gunning for that high score in a clan match where every FPS counts.
It seems as if all large memory manufacturers/suppliers are afraid to lose face by not pumping out high speed memory modules with lax memory timings just so they can list them in their product lines. Many enthusiasts I know, tend to favor slower memory which allows them to run aggressive timings however.
One might say that benchmarks we used were stacked against memory that uses conservative timings, but if you think about it, games and simple 2D applications are programs that most consumers run where speedy performance really is important. That's why we ran benchmarks we did; office environments with their servers or workstation PC are more interested in stability, and overclocking has an element of risk involved for both hardware and software.
Athlon64 based systems seem to act a lot like 800 MHz FSB Pentium 4 processors in regard to their memory bandwidth and timings when overclocked. However, before conclusions can be drawn in this field, more research has to be done before....
If you're in market for new memory for your Pentium 4 system and you're only thinking about gaming performance, then you're best bet is to get DDR which is rated to run aggressive timings. Some examples include Mushkin's PC3500 Level II which is rated to run 2-2-2-5 at 217 MHz FSB or Corsair's TwinX-3200LL which are rated for 2-2-2-5 at 200 MHz.
If you're a newbie/novice overclocker and would prefer to buy something that takes a little less work while still producing good numbers on your Pentium 4 system, then by all means get some of high speed DIMMs that are available on market. They're not quite as fast as low latency modules as we've shown, but they're much easier to set up. Now for AMD systems, because AthlonXP cannot hit as high speeds as Pentium 4 in general, it is always best to pair an AMD processor with nice low latency memory for best results.
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