What is Memory CAS Latency ?

[Anek]

hello friends,

I want to ask what is memory cas latency ? Can anybody please explain me and provide the useful information regarding this ...!!!

thanks a lot

[Russell]

CAS stands for Column Address Strobe

CAS Latency (CL) is defined as the delay time that elapses between the moment a memory controller tells the memory module to access a particular column in a selected row, and the moment the data from the given array location is available on the module's output pins.

• In asynchronous DRAM, the interval is specified in nanoseconds.
• In synchronous DRAM, the interval is specified in clock cycles,
  which must be multiplied by the cycle time (i.e. divided by the clock frequency) to convert to nanoseconds.

[Joshua]

CAS refers to Column Address Strobe or Column Address Select.

Data is normally accessed sequentially (same row). As a result, the CPU only needs to select the next column in the row to get the next piece of data. In other words, CAS Latency is the delay time between the CAS signal and the availability of valid data on the data pins (DQ). The latency between column accesses (CAS) then plays an important role in the performance of the memory.


Lower the CAS latency, Better the performance and vice-versa.

[PeterAGASSI]

CAS latency determines the number of CPU wait states between column address operations, hence a lowered CAS latency value is better and preferred.
Most quality RAM operates at CAS 2, while the largest portion of cheaper generic memory often requires CAS 3 for stable operation.