Front side bus<->cpu

[Guest]

I know that the front side bus is multiplied by the clock speed of the cpu to get its actual speed, but doesn't the fsb run at what your system's memory runs at? The duron has a 200 fsb, but can this be achived with pc-133 ram, isn't pc-133 133 mhz? I'm confused. I basically want to know exctly what front side bus is and what it does. : )

 

[Guest]

The memory on the via-boards can run non-syncron to the fsb. My durons fsb runs 100mhz (ddr), and the ram has been added the pci-bus speed witch is 33mhz (one thrid of fsb).
This means that if you overclock your fsb to 110, your ram will run 110 + 110/3 = 146mhz witch is too much for most ram. You then have the choise to reduce the ramspeed to the fsb witch would be 110.

 

[starbucksaddict]

Think of the whole situation as eating dinner.

the L1/L2 cache is your mouth
CPU speed is how fast you can chew and swallow
memory is your plate
FSB is the speed of your hand/fork

most CPUs run at 100 or 133 FSB
athlons are "double pumped" i.e. they use two hands
the reason that CPUs with 266 FSB are not twice as fast
as 133s is that
a)you can't chew that fast
b)you only take something off your plate when your mouth is empty
c)if you can't find what you want on your plate,
you have to order it from the slowest waiters on the planet (the hard drive).



Flame not, lest ye be flamed.

 

[mpjesse]

I think your confused on the whole "DDR" thing. DDR is a way of doubling bandwidth on a clock cycle by sending 2 bits of data instead of one. This is done on the rise and fall of each clock cycle.

So, a 200mhz FSB on a Duron/Athlon is really 100mhz doubled (hence, it is sort of 200mhz). The whole idea is that if you can send two bits in one clock cycle you are really doubling the clock speed.

And yes, the FSB is the speed at which the northbridge and memory operate at. After the northbridge processor is gets slower- AGP is 66mhz, PCI is 33mhz, etc.

Now, don't confuse DDR with the P4's "quad" bus which supposedly runs at 400mhz. Intel decided not to go with DDR and just make 4 pathways for data that all run at 100mhz all going to the memory and northbridge. The problem with this is your not actually getting any speed advantage, rather your getting a bandwidth advantage. I personally think the quad bus design is a little flawed because it's still limited to 1 bit per clock at 100mhz.

-MP Jesse

"Signatures Still Suck"

 

[munkey]

nice anology. but what i did with my Duron 850, after unlocking the multiplier i lowered it to 6.5 and raisede my bus speed to 133(DDR). even though it was only a 14MHZ increase in clock speed i got the higher memory bandwidth to raise all my benchamrks in sandra fom just barely competing with a pIII 750 to T-Bird 900. anyways that is what i did that seems to work great.

is this reality... i thought it would more realistic.