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Cas Latency

post #1 of 6
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Can someone explain what Cas Latency is to me please? I am trying to get me some new memory and I dont know what that is. I only have 1G now, and I want to go ahead and get 4G total (2stick of 2G each). Thx.

Also, I noticed some memory comes with a fans for it. How do you know when you will need a fan blowing rt on your sticks?
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post #2 of 6
http://www.overclock.net/intel-memor...html#post87996
post #3 of 6
The lower the latency is, the less time it takes to fetch data from the sticks. A PC6400 set with 4-4-4-12 would be considered pretty good.

You don't need a fan over your ram unless you intend to push the voltage of it to 2.4v or higher (very high performance ram).
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post #4 of 6
Quote:
Originally Posted by Acoma_Andy View Post
The lower the latency is, the less time it takes to fetch data from the sticks. A PC6400 set with 4-4-4-12 would be considered pretty good.

You don't need a fan over your ram unless you intend to push the voltage of it to 2.4v or higher (very high performance ram).
well then how come that expensive ram something like ddr3 with timings on like 7-7-7-20 is considered good?
    
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post #5 of 6
Quote:
Originally Posted by umopp View Post
well then how come that expensive ram something like ddr3 with timings on like 7-7-7-20 is considered good?
Because DDR3 has faster speeds then DDR2.

DDR had a max speed of 200Mhz and a standard CAS of 3-3-3-8

DDR2 had a max speed of 400Mhz and timings between 4-4-4-12 to 5-5-5-15

DDR3 has a max speed of I don't know what and timings starting at 6-6-6-18

The pure speed makes up for the latency.

(note that these are the JEDEC max speeds, and that since it's Double Data Rate, you mulitply the speed by 2 to get the final speed)
Edited by Locool676 - 8/21/08 at 4:52pm
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post #6 of 6
Its a balancing act between timings (4-4-4-12) and MHz speed (bandwidth). A performance measuring program like Everest, SiSoft Sandra, orSuperPi can show you the differences as you change your timings/speed. Most Intel processors like the bandwidth more than lower timings. Many sticks of 1066 5-5-5-15 RAM,will also work at 800 4-4-4-12.
Most 2x2 kits do not run hot and won't need a fan.
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