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CAS latencies

Jul 13, 2007
  1. i'm planning a new build after intel's pricecut, and i was looking at RAM, and i couldn't help but wonder, is there a major difference in speed between DDR2 800 with CAS latency of 4 vs DDR2 800 with CAS latency of 5? is it worth the extra $30-40 to get the lower latency.

    and what about the difference between CAS latency and 4 and CAS latency 8, cuz that's what i have right now (built my current machine right after DDR2 came out, so that's all there was)?
  2. Grafficks

    Grafficks TS Rookie Posts: 302

    Memory latency is defined as the length of time between sending a request and receiving the response. Low-latency memory is more responsive than high-latency memory. You can determine a RAM module's latency values by a string of four numbers (also called timings) in its spec. It's enough to know that the four different numbers represent four different portions of the finding and retrieval process. For instance, a memory module spec'd at 4-4-4-12 would take less time to respond (would respond faster) than a module spec'd at 5-5-5-15.
    Make sense?

    And CAS Latency is just the first number in the string of four numbers. The first number in the RAM's latency spec is the most important.

    Basically, the lower the better. You'd prefer DDR2-800MHz RAM with a CL (CAS-Latency) of 4 rather than 5.
  3. CMH

    CMH TechSpot Chancellor Posts: 2,039   +9

    You may be able to see the difference between CAS4 and CAS5, but it'd be a very limited difference, and you'd probably have to be on the lookout for it.

    If you're going to overclock, having a lower CAS will help reach higher overclocks.

    Grafficks has given a very good explanation of what CAS is. If you're going to upgrade to a CAS4 from a CAS8 just for the performance boost, I'd say save your money. If you're going to use your CAS8 RAM with your new CAS4 or 5 RAM, I'd say save your money. Your RAM will run as fast as your slowest RAM, so if the slowest is CAS8, your CAS4 RAM will still run as CAS8.
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