Memory clock differs in GPU-z and MSI?

[Chintan Dave]

I have gtx 660.I n gpu-z the memory clock shows 1502 mhz, while in MSI it shows 3004 mhz. I'm really confused. What is my actual mem clock? Core clock is showing same in both i.e 1202 mhz. But why is there a difference (SO BIG DIFFERENCE) in mem clocks?

 

[TJ Hooker]

VRAM has a reference clock, which is then doubled. 1502 is the reference clock, 3004 is the effective clock. Different utilities will report different clocks. Also, data is transferred on both the rising and falling edges of the clock signal, so the effective transfer rate is doubled again (i.e. 6008).

To be a little more accurate (from wikipedia): "GDDR5 operates with two different clock types. A differential command clock (CK) as a reference for address and command inputs, and a forwarded differential write clock (WCK) as a reference for data reads and writes, that runs at twice the CK frequency."