RAM capable of CAS 2, what does it mean?

Discussion in 'Hardware' started by Runningbear, Sep 1, 2003.

  1. I see a lot of DDR RAM comes with a CAS rating, can anyone tell me what this means and how it effects RAM performance?


  2. omcate


    Q: What is the "CL" that I see listed in memory specifications, especially with premium-priced, "high-performance" memory?

    A: Time to get a bit technical. CL stands for CAS (Column Access Strobe) Latency, which is the amount of time that the PC will wait before retrieving data from the RAM. CL2 modules need the PC to wait two CPU clock cycles before getting data; CL3 modules need a delay of three clock cycles. CL2 memory is more expensive than CL3, but your motherboard must support the faster modules. The CL speed is programmed into the memory module and is automatically detected by the setup program's SPD (Serial Presence Detect) when you boot the system. If the PC detects a CL2 memory module and can use it, the speed will be set automatically. A CL2 memory module will work in motherboards that support CL3, but not at its maximum speed. In most cases, you don't need to be concerned about CL when you're purchasing memory, as long as you order modules specifically designed for your PC's motherboard.

  3. nitro


    On highly pipelined architechtures like the Opteron or P4 Xeons with Hyperthreading, the extra clock cycle non-delay would be worth getting.

    On the other hand, if your CPU has a large cache, e.g. >1MB like the Xeons, the extra wait state is not as critical.