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- overcloking novice questions
July 17, 2005, 9:50 pm
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Re: overcloking novice questions
| I've a question:
| What does mean the Memory latency?
| Where can I find the latency of my memory ?
| What is the signification of 3-4-4-8 timings for example ?
| Thanks a lot for your help.
A short, simple, answer:
The numbers represent delays caused by various functions in memory access
between requesting data and presenting valid data as a result. This has
nothing to do with the delays caused by the CPU clock being so much faster
than the Memory bus clock.
When overclocking memory (running it faster than the manufacturer
specifications), a faster clock speed can sometimes be gained by increasing
the settings for the latency timings. Of course, this will cause a slightly
longer delay before the memory presents valid data in response to a request.
It's a tradeoff that may or may not be worth it.
Because of large speed difference between the CPU clock and the memory bus
clock L1, L2, and sometimes L3 caches are used to help reduce the effect of
delays. Because of this the performance increases of memory are not as
large as you might think (when required data is alread in a cache, delays
are short.) If, for a certain application, data is found in a cache 90% of
the time, even doubling memory speed will show only a 5% improvement in
performance. The most important use for increasing latency settings for
overclockers is that the only way to overclock Intel CPUs is to increase the
CPU clock speed, and consequently, the memory bus speed. Increasing the CPU
clock speed shows a comprable increase in performance for applications where
data is found in the caches a large percentage of the time.
If you have a overclocking friendly motherboard, the BIOS should display
memory latency timings, and allow some to be reset.
In a module (stick) of memory, a small read only memory chip contains the
latency settings and other requirements for the memory operation. THESE
SPECIFICATIONS MAY NOT BE THE SETTINGS THE CHIP MANUFACTURER DESIGNED FOR.
Manufacturers of memory modules who don't manufacture memory chips sometimes
slect chips from a bin by testing, then set the specifications so that the
chips are automatically overclock when installed. This can be either a good
thing or a bad thing, depending on the diligence of the manufacturer.
The motherboard in all this is key. If the motherboard is not overclocking
friendly and is not well designed and manufactured, then overclocking
usually is a very frustrating experience. If the motherboard IS
overclocking friendly and IS well designed and manufactured, then,
especially for Intel chaips, overclocking can be very easy, with a 50%
overclock easily possible for certain speed chips (usually those in the
middle of the speed range for the model .)
I am sure more techincal information will follow.
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