memory stick+what is CL3

July 27, 2011 at 15:00:57
Specs: Windows 12.09.2009, AMD Athlon 3400+
I'm getting ready to add some memory. Originally installed 512MB PC3200 DDR 400MHZ, 2 sticks; I want to increase with a couple of 1GB sticks, I find the above with "CL3" after it. What does the "CL3" mean, and can I use it??

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July 27, 2011 at 15:36:48
Most ddr ram has a cs latency of 3. The lower the number the faster the ram can handle the request. I doubt you would notice the difference between 3 and 2.5. You better check your mobo specs before you buy the ram. You can check it at Use the scanner on their page.

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July 27, 2011 at 18:41:13
"Column Address Strobe (CAS) latency, or CL, is the delay time between the moment a memory controller tells the memory module to access a particular memory column on a RAM memory module, and the moment the data from given array location is available on the module's output pins. In general, the lower the CAS latency, the better."

See the "Memory timing examples (CAS latency only)" table

The memory module is first accesed in 15 nano seconds for DDR ram with a CL of 2.5 or 3, and there's very little difference after that

Once the memory is initially accessed, there is no difference between the performance of ram that has different CL ratings, if the modules have the same specs otherwise.

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July 28, 2011 at 12:42:59
Thanx to Grasshopper and Tubesandwires - big help; but now another dumb question (my wife says no such thing). The memory is going onto an ASUS A8V motherboard I built fm barebones kit. four memory slots, A1&A2, B1&B2. Book says for single channel, populate B1 first; dual channel, B1 & A1 or all four slots. Can I get away with: a 1GB stick in A1 and B1, and 512MB sticks in A2 and B2??? Or all 1GB in B1&B2, 512's in A1 & A2; or don't mix???? How do I mix and match, or should I not do it??

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July 28, 2011 at 13:20:46
Dual-channel mode can improve performance a little bit. But you'll need matching pairs of sticks for each channel.

Seeing how you do not have matching sticks of 1GB, the whole thing will be running in Single Channel mode.

You should be able to put your matching 512MBs in A1 & B1, and your new 1GB in A2 or B2.

And Bob's your uncle!
Let me know how you make out.

PS: The manual notes that you may have issues with 1GB modules:
- if the memory chips on the RAM stick are 128MB each
- if they have 16 memory chips and are on both sides of the stick (8 chips per side).

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July 28, 2011 at 14:00:59
"Dual-channel mode can improve performance a little bit"

I agree.
Running pairs of modules of the same capacity in dual channel mode is just another one of the things that is much better in theory than it is in the real world.

You are unlikely to be able to tell the difference between the ram running in single channel mode vs. dual channel mode, mostly because it only makes a difference when a program actually benefits from more bandwidth - a higher max data transfer speed - being available, and is actually using it. Most of the time, your computer is NOT using anywhere near the max bandwidth the ram is capable of using.

All the installed modules must be running in dual channel mode, otherwise all of them run in single channel mode,

The ram pairs of the same capacity running in dual channel mode can be matched pairs, which ensures they're identical, or two identical modules, e.g. that have exactly the same part number.

"PS: The manual notes that you may have issues with 1GB modules:
- if the memory chips on the RAM stick are 128MB each
- if they have 16 memory chips and are on both sides of the stick (8 chips per side)."

You can avoid buying the wrong ram modules by NOT buying it randomly.
If you use your mboard make and model to search with on a ram manufacturer's or ram distibutor's web site to look up which ram is listed for your model (works in your model; is compatible with your model) you can't go wrong.
If it's brand name ram, once you know which module part numbers are compatible with your mboard model, you can buy them from anywhere that has those part numbers.

If you already have ram mof the right type e.g. DDR2, it does no harm to try using it, but it MAY not be recognized properly. If it's not recognized properly, there's probably NOTHING wrong with it - it will work and be recoginized fine in a mboard it IS compatible with.

If it's brand name ram, you can look up the ram for that brand to see if the part number of the ram you have is listed.

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