FSB Strap...

V3g3tto

V3g3tto

V3g3tto

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Before i ask what is probably a blindingly obvious question to some, yes i've read the guides/stickies,etc. :p

Just what exactly is the FSB strap in my bios? I have a P5K mobo, and my OC choices are initially upping the FSB frequency, then choosing from a list of 1:1 ratio DRAM frequencies below it (unless i manually +/- it). Between this is the Strap setting however, what exactly is this? As far as i understand it in the most basic terms:

FSB Frequency- The speed of the bus between the processor and memory (i think..), increasing this increases the information passed along it. Multiplying this by 4 gives you the actual total FSB (in my case with 333mhz, the FSB is 1333mhz).

DRAM frequency - Obviously the speed of the RAM and ideally, being DDR, is twice that of the FSB to give a 1:1 ratio (which i think makes it a lot more stable?).

So what the hell is the FSB Strap? i got choices between 166mhz and upwards. I see endless mention of the RAM divider (damn lingo),etc, but no mention of what this setting actual does. Anyone able to explain? Also, am i partially right in what i said above?
 
As I understand the terms:

FSB (front side bus [speed])- Speed of northbridge
DRAM Frequency - Speed of RAM (not to be confused with RAM timings which are the latancy of different RAM opperations)
FSB Strap - A series of timings that dictate the latancy of the Northbridge

CPU Speed = Multiplier x FSB

Looser straps may allow higher FSB and looser timings may allow higher RAM frequencies. Tighter straps may give better performance at the same FSB and tighter timings may give better performance at the same RAM frequency.

A divider is where the RAM runs at a different speed to the FSB. This is generally bad for overclocking (stresses the northbridge a lot) and comes with a performance overhead that may outweigh running the RAM our of sync in the first place.
 
Ahh ok thanks. Doesn't seem i need to pay too much attention to it then and can leave it on auto.

As i see it then, i shouldn't need to touch the strap at all as my mobo should walk over 400mhz FSB. Also shouldn't need to loosen my timings as i only wish to push RAM frequency to around 800Mhz.

Ahh so by RAM divider they basically refer to the ratio. i.e. 5:6 (FSB:RAM) ratio would be 300 FSB and 720mhz RAM. This of course increases the speed of the RAM, however in my case would kind of bottleneck as the FSB is not high enough.

From what i can see, the only reason anyone would want anything but a 1:1 ratio, if i read this right, is if their motherboard doesn't support a high FSB.
 
Putting RAM higher is common but of questionable value - it can cause instability and the overhead of running the devider often isn't worth the extra RAM speed.

Running RAM slower makes sense if the RAM would otherwise hold your overclock back. This can be worthwhile but since RAM is so cheap it's much better just to go buy some better RAM.
 
In theory PC6400 RAM is fine for most as to run it at it's optimum speed of 800mhz, you really want a motherboard supporting an FSB of 1600mhz (i.e. upping it to 400 in BIOS) and since the vast majority of boards require you to OC to reach that FSB (except some X38 boards i think), higher RAM speed can only be justified if you plan to knock on 4Ghz territory.

...i think..

Edit: i'm wrong, completely wrong, ignore me :)
 
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V3g3tto said:
So what the hell is the FSB Strap?
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It's something I have never fully understood and since upgrading to a P5K-E myself it has been left on auto but time permitting I will adjust it and see what happens.

The FSB strap is meant to be improved on the P35 chipset compared to the older P965 chipset, on that anytime you raised your FSB above 400MHz the FSB strap would auto adjust down, the main effect of this that I noticed was my memory bandwidth was greatly reduced but the system still ran stable etc.

I think the NB Strap is some form of divider for the chipset, if the FSB is set too high for the chipset the strap can reduce these speeds so that the chipset doesn't freak out.

I remember reading up about this on xtreme systems and there was also some mention of the fact that when you use a CPU at its non default divider (i,e reducing it from say x9 to x8) this also increases the strain on the northbridge.

I would view the strap setting as another variable in your overclocking tool kit, if you are having problems hitting a big overclock with the strap on auto then I would consider adjusting it manually to see if it improved things.

Hopefully someone who more knowledgable than me on the subject can comment further. . . .
 
I see,hmm that is interesting.

Seems on high overclocks it will need to be looked at in some form, if it's like a fail-safe setting.

I'm confused as to why anyone would want to put down the CPU multiplier though, surely that means a higher FSB needed, meaning lower OC.
 
Sometimes lowering the multi can give a higher overall overclock on the chip. It's for when the overclock is limited by the chip - not the motherboard (NB).
 
V3g3tto said:
I'm confused as to why anyone would want to put down the CPU multiplier though, surely that means a higher FSB needed, meaning lower OC.
Click to expand...
Firstly reducing the CPU multiplier is a good thing to do when you are testing to see how high an FSB your motherboard can run, by taking the cpu out of the equation you can focus just on the chipset, which is pretty much the first thing I do when testing a new motherboard.

Secondly some people have a processor that isn't able to hit an uber overclock but the chipset and memory is willing, in this scenario it helps claw back a little extra performance by pumping the FSB and memory as high as it will go. . .

Example E6600 (9x266) can only run at 3300MHz before becoming unstable

9 x 367MHz = 3303MHz

but by reducing the chips multi you could also run:

8 x 413MHz = 3304MHz

7 x 472MHz - 3304MHz
 
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Hmm will test that. First things first though, auto seems to have put my vcore at 1.41v with just a 333mhz fsb, gonna try whacking that down a couple of notches.
 
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