Hi all,
I just have some fun with DQS Strobe timing

The DQS signal has several characteristics:

DQS is bi-directional

A DQS line is typically generated for 8 lanes of data from the DDR memory

The phase of DQS relative to the data depends on the operation being performed (Write or Read)

DQS is not free running

In the memory device, DQS is generated by DLL to minimize the skew between it and data

DQS has a Preamble state just after the signal comes out of tristate where DQS goes low

DQS has a Postamble state just before returning to tristate where DQS goes low

So according to this, let see some real benches:

Testbed:
CPU : AMD FX55, Mach II cooled
Mainboard: DFI NF4 SLI-DR (BIOS 310)
OS: Windows xp
Ram: GSkill 1gb LE DC Kit
Video card: X850xtpe, Water cooled
PSU: OCZ power stream 600adj

**please note: in BIOS if you choose increase, that would show "slower" in A64tweaker ;if you set decrease in BIOS, A64tweakerwould show faster

First of all let's see DQS off:



DQS slower ;skew:128, super pi 8m is a bit faster than off



DQS faster; skew:128, it's slower than off.



Summary:

DQS skew Control--->Increase for performance, and Decrease for Stability.

DQS Skew Value-->the value that is Increased or Decrease when you set the DQS skew control. This is not a very sensitive timing wecan try 50~248
Both are slight influence on bandwidt and stability.