Motherboard bandwidth and CPU's?

[Passions]

So I was arguing with a friend today, he says that it doesn't matter with a P4 1.7ghz it will run the same as like a P3 1ghz, since the motherboard runs at 133mhz. I was saying huh? I doubt you could tell the difference considerably but there is still a definate difference between the two. Then, he goes off about the bandwidth of the mobo being so slow, data cannot go fast enough, the 1.7 is exactly like a 1ghz, blah blah blah. I donno what to say to him.

Then another time, a friend said that whats the point of a cpu being like 900mhz, when the motherboard only runs at 133mhz, so the cpu only runs at 133mhz too. All that extra mhz is wasted and cannot be used since the mobo only can run at 133mhz. wtf?

I did not have good answers to these questions, can someone give a detailed explanation? Sigh.

 

[MichaelD]

This definitley is not the be all end all explanation (where is WingnutPez when 'ya need him? ) but you're friend has rocks in his head. The P4 has a quad-pipline memory bus, whereas the PIII has runs a "normal, not mulitiple data rate) memory bus. The P4 can push 4x the info a PIII can.

That's about as far as I can go. So, my reply is basically a bump for your good comparo question! Someone else help me show him what a rockhead his friend is.

 

[gopunk]

your friends are forgetting the multiplier.

 

[gopunk]

http://arstechnica.com/cpu/2q99/clock-intel-1.html

enjoy

 

[BurntKooshie]

The next time your friend talks about computers, and how they work, ignore them.

 

[gopunk]

how old are your friends? sounds like they're living in the days of the 486. read the article and skool them

 

[MustPost]

wait doesn't the P4 have a 100MHz Quad pumped FSB equivilent to 400MHz or something. That means by your friends logic a P4 should be like 3 times faster than a P!!! running at 133 FSB

 

[Passions]

well im not really conserned about the p4 vs p3 part, i was more thinking about the motherboard fsb part. he said that since all pentiums basically run at 133mhz fsb, the speed in 1.7 p4 and a 1.3 p4 doesnt matter. :|

 

[gopunk]

<< well im not really conserned about the p4 vs p3 part, i was more thinking about the motherboard fsb part. he said that since all pentiums basically run at 133mhz fsb, the speed in 1.7 p4 and a 1.3 p4 doesnt matter. :| >>


did you read the link i posted? you'll find your answer there.

 

[MustPost]

You have to use his own faulty logic against him, im telling you

<<wait doesn't the P4 have a 100MHz Quad pumped FSB equivilent to 400MHz or something. That means by your friends logic a P4 should be like 3 times faster than a P!!! running at 133 FSB>>

By his logic A P4 should be 3 times faster than a P3. Since he claims there equal youve proven him wrong. And since P4s arn't 3 times faster than P3s his whole story falls apart

 

[NelsonMuntz]

The FSB is not the only determining factor in how quickly information is processed by your computer. It is merely the path getting it too and grom the cache on the CPU. The size of the cache makes a difference as well (performance difference between equally clocked Durons and Athlons or equally clocked Celerons vs. PIIIs). There is also the consideration of prefetch and instruction sets. Plus, as others have mentioned the bandwidth is different for PIVs vs other CPUs. If the FSB were the limiting factor in all processors that used the same FSB, then you would see no performance difference between say a PIII 533 MHz CPU and an Athlon 1.4 GHz, but as we all know there are HUGE differences in performance between these two.

 

[BFG10K]

So I was arguing with a friend today, he says that it doesn't matter with a P4 1.7ghz it will run the same as like a P3 1ghz, since the motherboard runs at 133mhz

That's wrong on a number of levels.

Firstly, a P4 has a 400 MHz FSB and 800 MHz dual-channel RDRAM. The RAM bandwidth is 3.2 GB/sec.
A P3 has a 133 MHz FSB and 133 MHz SDRAM. The RAM bandwidth is ~1 GB/sec.
So the P4 has four times the FSB bandwidth and three times the memory bandwidth.

Secondly, the P4 has been optimised for high bandwidth situations, while the P3 has not. Therefore putting a P4 on a 133 MHz FSB and RAM will make it behave very differently to a P3 in the same situation (and likewise putting them both in a high bandwidth situation will make them behnave differently) so it's essentially an apples vs oranges comparison.

 

[elkinm]

Whell, the P4 has the quad pumped FSB making it at 400 MHz as opposed to the P3's 133, but don't forget that the P4 is highly dependant on that memory bus and bandwith as with PC600 ram as oposed to PC800 or the upcoming PC133 and DDR chipsets the P4 is cripled. Also the P3 would destroy a P4 at the same bus speed and clock speed but that won't happen. The memory bandwith between the 1.3 GHz and 1.7 GHz is almost the same, but the 1.7 has a slight range as long only it's 256 L2 cache is used. The P4 is strange and is disapointing, but at the current speeds it is slightly faster then a P3 for many reasons.