Why does using a strap make a difference?

[Ambidexter]

Hi,

I have an M6F and am trying whatever I can to get it OCed well with my 4770K.

When I started using a 125 strap yesterday, I notice it may run a bit cooler on my custom WC, but I wonder what else it's doing.

What is different on the board or cpu if I have a strap of 125 and a multiplier of 32, vs. a strap of 100 and a multiplier
of 40? Both are clocking the CPU at 4000 MHz. I guess the PEG/DMI is different, it seems easier to get the uncore
working where I want it...but why?

Thanks,

-Ambi

[Doug2507]

Good question and something i'm keen to find out as well. My current board (non asus) doesn't like changing strap one bit so looking forward to seeing if the M6E makes a difference.

Apart from giving more variety in clock speed for ram does it help max core clock / lower vcore or is this a bit of a myth? Is it purely just for better choice of freq for ram? If it does help with core what's the technical reasoning / explanation behind it?

[Raja]

Should have no difference on temps assuming you've set everything manually and not left any contributing rail voltages on Auto (where they could possibly change). That is assuming that all domains are running at the same clock speeds between both straps as well because current draw is proportional to frequency.

Other than that, changing a reference clock can impact downstream signal timing margins - for the better or sometimes for the worse. Stability and the voltage required to run a particular frequency depends upon that margin. The more margin one has, the less voltage is required to get the system stable (voltage variance between two different reference clocks is not necessarily large though).

-Raja

[Doug2507]

Cool, cheers Raja.

[Ambidexter]

It may also help our memory reach its best overclock. The bclk is also used for the memory multiplier, isn't it?

Cheers,

Ambi

Doug2507 wrote:
Cool, cheers Raja.

[Ambidexter]

I suppose the obvious answer is that using a strap gets us "between" the standard multipliers. So if I'm stable at 46x100 but not 47x100, 37x125 would get me 4625, which may be stable, with the proper voltages. So, we should consider changing straps or bclk frequency only after we are certain the speed and voltages for stable vs. unstable are understood.

Regards,

Ambi