FSB Strap for noobs.

[Blauhung]

hmm, that actually seems to hint that the bulk of the performance there is from the pre-fetching on the CPU. I think i'll try CPU-z, even though I don't use it all that often cause if makes intel desktop util's not work.

[ooztuncer]

Please help me to understand/confirm couple of concepts:

In my mind there are 5 different settings need to be optimized:

i) chipset (NB) latencies (straps)
ii) chipset speed (800mhz, 950mhz, 1125mhz, etc)
iii) cpu speed (8x400, 9x400, etc)
iv) memory speed (bandwidth)
v) memory latencies (3-3-3, 4-4-4, etc.)

We know that chipset latencies (item i) are constant between intervals. For instance, chipset have tighter latencies up to 401 MHz than it is between 401-467 MHz. These intervals are called as straps. And these strap boundaries are different between boards. For P5b, upper boundary of 1066 strap is 400 MHz, as soon as you pass 400MHz (in bios) you are in 1333 strap. As far as I know, new RD600 will give us the ability to set our own strap boundaries – so that we can set the 1066 strap valid until 455 MHz (or whatever we want).

edit: {{{ I think terminology wise more correct version: 1066 strap latencies are valid between 1066-1600 mhz; 1333 strap latencies are valid between 1601-2000 mhz, etc. }}}


We assumed that as chipset speed (item ii) increases we will have a faster system overall. However, as soon as we move into next strap overall system speed actually deteriorates until a threshold fsb is achieved. That’s why 9x400 with tight chipset latencies is faster than 8x450 with loose chipset latencies. The question is where can we see the real performance increase in the next strap (what is that threshold value)? Is it at 450mhz or 500mhz, or better, can we measure it by percentages? Let me explain what I am trying to say, if 1066 strap’s boundary is 400 fsb, then what percentage we need to pass to see a real performance increase? If the answer is 15% then we will have a faster system by running 8x450 (using some type of async settings to set fsb = 920mhz - 15% increase then 800mhz) then 9x400 (fsb = 800mhz). By this way, we can use our magic formula in every board that doesn’t allow us to change the strap boundaries.

Then we have the cpu speed (item i). Can there be a practical guide which will tell us which one is better up to what point: higher cpu speed with loose chipset latencies or lower cpu speed with tight chipset latencies, like 8x475 (3.8ghz) or 9x400 (3.6ghz)? This is slightly different than above paragraph because above we were comparing 8x450 (3.6ghz) against 9x400 (3.6ghz).

Memory bandwidth and latencies (item iv and v): as we know, the faster the better - in benching or psychologically in daily tasks But really, in order to achieve the fastest (best balanced) rig which one should we more focus – memory bandwidth or memory latencies? Is it a good idea to run 5-5-5 at 1300mhz or 4-3-2 1000mhz (like old bh5 versus tcdd comparison)? Which is more important in LGA 775 platform > latencies or bandwidth?

I believe this is the fun part of overclocking > testing and trying to find best (fastest) combination. And probably it is unique for each rig… But I would like to hear comments from people that already found their combination

Thanks…

[ineedaname]

So if you are running a E6600 (266 * 9) at 400Mhz x 8 your NB FSB is:

(9 / 8) x 400 = 450Mhz FSB (1800Mhz Total)

Is it just me or is that calculation wrong? I have no clue where you got 450 from. At (400 x 8) your NB FSB should be 1600. I think you made the calculation more complex than it really is. The NB FSB has nothing to do with the CPU multiplier it is just the FSB x 4. (400 x 4 = 1600)

[alexanderhuzar]

To the north bridge, you are always at a default multiplier with a Extreme Edition processor. This allows you to set a much lower or higher multiplier without the NB FSB being effected.

Noob question alert!

Does this mean that Intel is fu*king us up the as* with cheap chips? Or can you change the Strap manually if you have a good motherboard?

[aoch88]

What happens if my motherboard does not have this strap settings?