(Confused) P4/AMD FSB RAM Myth?

[Wiz4rd]

As someone who has never owned a pentium based machine, I'm somewhat confused. As I look around I see these P4's running like 800 mhz fsb and I'm like, what the hell. Why do P4's memory and fsb run so high? AMD's 400mhz fsb is what I'm running now. I always bought AMD because I figured you get the same performance at a cheeper price. I mean cpu to cpu AMD keeps right up, but this memory and fsb thing is strange. Do intel boxes really run a front side bus of 800 mhz or even faster? And if they do, are the boxes even faster than AMD?

I also see P4 users buying ddr400 ram instead of rambus which REALLY confuses me more. I would really appriciate someone with some knowledge of both machines to clarify this. Thanks guys.

 

[zabomb4163]

p4's are quad pumped

533bus on p4 equates to 133*3

when somone with a p4 says they have 800 bus, the ram is running at pc3200 speeds. get it?

 

[Wiz4rd]

Oh ok, so there isn't really any performance improvements.

 

[-=TriX-R4-KidS=]

for memory bandwidth happy apps there is...

fsb speed is doubled when compared to an athlon....so the p4 has that extra fsb on the P4 can use the Ram bandwidth(in theory at least).

as i understand it....

FSB Dual Channel DDR400 RAM bandwidth
-----------------------------------------------------------------------
AMD 2x400 (400) 400x2 (800) -- CPU only used 1/2

INTEL 4x200 (800) 400x2 (800) -- CPU uses all bandwidth

The athlon cannnot utilize all the RAM bandwidth....where as the P4 can.

 

[Wiz4rd]

SO would it be smarter to purchase a AMD cpu with 333 fsb rather than the 266, and if so what can one expect for a performance gain?

 

[-=TriX-R4-KidS=]

yes it would

it varies....but youd be gaining 25% in usable memory bandwidth....id guestimate a performance difference around 13%

take a look at the athlon benchmarks here: http://www6.tomshardware.com/cpu/20021001/xp_2800-13.html

the 166fsb gave the athlon quite a bit ofa boost.

-TriX

 

[ninthebin]

you can expect anywhere from about 1 - 20% depending on what your doing...

on matter of why P4 users arent buying rambus, well it has kind of lost support if you notice the I875P chipset dubbed the successor to the I850E uses DDR. But this is ok, as you can now run DDR in Dual Channel mode which will give you "double" the bandwidth.

http://www.anandtech.com/chipsets/showdoc.html?i=1806

perhaps this article may help, it discusses the FSB gain from 533MHz to 800MHz in a P4 system, you can take its observations generally for FSB increase.

 

[InThrees]

SO would it be smarter to purchase a AMD cpu with 333 fsb rather than the 266, and if so what can one expect for a performance gain?

Well, it would be SMARTER to purchase a 266fsb athlon and then crank it up to 333 or 400, and save some money.

Currently, with the quad pump, a number of pentium IV setups do have better memory bandwidth than their specific athlon competitors... But then again, at each level the Athlon system is generally less expensive, and the difference in performance is really not that great overall. In many cpu intensive tasks, the athlon will win... in SSE2 enabled tasks, the PIV will win...

But really, owners from both camps are generally happy with their rigs, and sure that they have the best.

 

[attack]

Well, it would be SMARTER to purchase a 266fsb athlon and then crank it up to 333 or 400, and save some money.

.....

But really, owners from both camps are generally happy with their rigs, and sure that they have the best.

Heh true that to those two statements!

I buy AMD because for the cost of a good high end p4 mobo you can get a XP1700 and nforce2 mobo for the same price. I like upgrading a lot, and with limited money in order to upgrade frequently I need to purchase less expensive parts.

AMD and Intel both have pro's and cons, right now intels pro is memory scores, AMD's is cost.