P4 FSB Question

[VIAN]

Say I have a P4 with a 533MHz FSB. What Speed RAM would you pair with it?

 

[Corporate Thug]

pc2100

 

[skrjones]

The 533Mhz FSB is a Quad Pumped 133Mhz speed which is why PC2100 is needed.

But if you are looking to OVerclock I would look at PC2700 (166) to give yourself an overhead.

 

[VIAN]

but doesn't it have 533 total Megahertz. 4x133 effectively equals 533, just as ddr200 effectively equals 400. What is happening with those other pipes if only one is being used?

 

[EarthwormJim]

You'll want atleast DDR-333 and run it at a 4:5 ratio (or if you get faster ram run it at a 3:4 ratio) with the FSB, thats what 845pe motherboards do by default. And what do you mean by extra pipes if only one is being used?

 

[VIAN]

Ok, 133 is quad pumped, that means that its 533, so shouldn't you be putting RAM on it that is 533.

EDIT: Yeah, I just went and did the research. It is true. It has a FSB of 533 and would best be paired with 533 RAM.

 

[Spike]

Originally posted by: VIAN
Ok, 133 is quad pumped, that means that its 533, so shouldn't you be putting RAM on it that is 533.

EDIT: Yeah, I just went and did the research. It is true. It has a FSB of 533 and would best be paired with 533 RAM.

As far as I know, 533 means you need DDR266 (pc-2100). The 800fsb boards use the DDR400 ram or pc3200. You can go ahead and spend a ton getting DDR533 ram, but that is going to do nothing for you really, I would get some PC-2700 (DDR333) so you can oc better if you want, but don't get DDR533 ram. Some of the other guys can hopefully explain it to you better than I did, but that is what I have been told

-spike

P.S. sorry for any confusion, I am a AMD boy so I just have to deal with confusing CPU speed numbers, not FSB

 

[Spike]

sorry for another post here, but this was pulled directly from intels website

"The Pentium 4 processor with 533 MHz system bus supports Intel's performance desktop processor by delivering 4.2 GB of data-per-second into and out of the processor. This is accomplished through a physical signaling scheme of quad pumping the data transfers over a 133 MHz clocked system bus and a buffering scheme allowing for sustained 533 MHz data transfers. "

link

That states in an almost clear way that the 533 systems run at an actual bus speed of 133mhz which means you would need pc-2100 ram (DDR266) as ddr is always x2 of the actual bus speed. (DDR = double data rate)

Hope that helps

-spike

 

[VIAN]

OK, let me put it this way. If you are only using 133MHz, then what about the other 400MHz? If you are only using 133MHz, then wouldn't DDR133 be too much? Understand that, 133 quad-bumped effectively equals 533, just as DDR133 effectively equals 266. So, for best performance, not that any board supports it yet - that I know of, you would need 533MHz RAM so that the RAM and FSB speeds can be synchronous.

I'm also an AMD boy, but I want to make sure I'm right on this manner.

 

[Spike]

Originally posted by: VIAN
OK, let me put it this way. If you are only using 133MHz, then what about the other 400MHz? If you are only using 133MHz, then wouldn't DDR133 be too much? Understand that, 133 quad-bumped effectively equals 533, just as DDR133 effectively equals 266. So, for best performance, not that any board supports it yet - that I know of, you would need 533MHz RAM so that the RAM and FSB speeds can be synchronous.

I'm also an AMD boy, but I want to make sure I'm right on this manner.

well, I don't know how to explain it in a techincal manner. I know that DDR266 is what you need for that setup and that unless you are going to change that base fsb of 133 to 266, DDR533 will not help you at ALL besides making your wallet a bit lighter. If you got DDR333 then you could push that fsb from 133 to 166 which I guess would give you a quad-pumped equivalent of 664mhz, but that is more speculation than anything. I am hoping someone who can explain the techincalites of it will post.

If you are still not satisfied I suggest emailing intel. They may be able to give you an answer that makes more sense. Just know that you are not wasting FSB and DDR266 (pc-2100) is the max you need unless you up that 133 base FSB.

-spike

 

[Duvie]

First off let me just say if you have a 533fsb you should run dual channel ddr and pair it with 2 sticks of pc2100....

At 4x133fsb for 533fsb the p4 has a theoretical bandwidth of 4.2gb/sec which is why yes on a single channel system pc4200 would be a perfect match since it is 533mhz ddr and 4.2gb/sec of bandwidth....However that being said you would need a ram ratio of 1:2 and frankly I have not seen that since the early P4 sis chipset days so you are shite out of luck running anything better then 3:4 or at 133fsb would be 166 for 333ddr or PC2700....So basically the best setup would leave you ony delivering 2.7gb/sec of memory bandwidth to a CPU producing 4.2gb/sec...Result CPU is bandwidth limited....

This is why a dual channel setup it more ideal....

2 sticks of PC2100 or 266ddr (133 x2) which equals 2 x 133 + 2 x 133 (2 sticks) for 533fsb....Or look at it this way PC2100 has 2.1gb/sec of bandwidth times that by 2 for 2 sticks and you get 4.2gb/sec of bandwidth...Perfect match!!!

 

[Spike]

Originally posted by: Duvie
First off let me just say if you have a 533fsb you should run dual channel ddr and pair it with 2 sticks of pc2100....

At 4x133fsb for 533fsb the p4 has a theoretical bandwidth of 4.2gb/sec which is why yes on a single channel system pc4200 would be a perfect match since it is 533mhz ddr and 4.2gb/sec of bandwidth....However that being said you would need a ram ratio of 1:2 and frankly I have not seen that since the early P4 sis chipset days so you are shite out of luck running anything better then 3:4 or at 133fsb would be 166 for 333ddr or PC2700....So basically the best setup would leave you ony delivering 2.7gb/sec of memory bandwidth to a CPU producing 4.2gb/sec...Result CPU is bandwidth limited....

This is why a dual channel setup it more ideal....

2 sticks of PC2100 or 266ddr (133 x2) which equals 2 x 133 + 2 x 133 (2 sticks) for 533fsb....Or look at it this way PC2100 has 2.1gb/sec of bandwidth times that by 2 for 2 sticks and you get 4.2gb/sec of bandwidth...Perfect match!!!

finally, someone who knows what they are talking about. Thanks for the reply, I was getting confused myself

-spike

 

[VIAN]

yay