Memory & Mainboard buses for P4. HELP!

I've heard that Pentium 4 processors work best with two clips of memory at a certain bus (do you know which it is?), so I thought "Great, I'll just buy my memory according to that bus!", but no...

My motherboard, Asus P4T, declares that it's "Max System Bus" is set to 100 Mhz, does that mean that you only can use PC100 memories? Can you use memories at all with 300 Mhz bus?

I also read here at this site that RDRAM is the preferred sort of memory for P4 CPU's, what if I had one old PC100 64 MB clip of memory and a brand-new RDRAM clip of 128 MB @ 300 MHz plugged in at the same time?

As you understand from these questions, I am a bit of a newbie on this area. It would be really nice if someone would cover the entire subject. I'm having a problem over here.

/ Topaz
6 answers Last reply
More about memory mainboard buses help
  1. The Crucial site has FAQ area and will match memory to your system.

    I wonder...what is the speed of gravity?
  2. Nope...

    Crucial's "Memory Finder" was no good for me, when I listed my motherboard, they said no components were availiable. I still have *no clue* what memory to buy... Thanks anyway...

    / Topaz
  3. Ok, here are the questions that would solve it all:

    • Why do *all* mainboards for Pentium 4 on this site have a Max System Bus of 100 or 133 MHz when both the CPU and the RDRAM have so much more capacity?

    • Doesn't the Max System Bus limit the clock of the memory to either 100 or 133 MHz?

    • What's Front Side Bus?

    / Topaz
  4. the p4 actually has a 100 mhz frontside bus but it is quad pumped thats why it say it is 400 mhz

    you have to use rdram in a p4 system and you have to buy two sticks of them at the same speed and same size
    get the 800 it is best performing don't even get the 600

    the front side bus is what you use to bassically set the speed of the prosscer like if you have a 1.7 ghz p4 then the mlutplier is set to 17 x 100= 1700
    also a higher fsb help out performance

    forntside bus is also the speed at which the cpu communicates with the main memory
  5. To second the above post, the RDRAM 800 is much better than the 600. RDRAM spelled out is Rambus DRAM. For all Pentium 4 boards, you must use this. Your old SDRAM will not even fit into a RDRAM board. You also must place each memory modle in it corisponding channels, unlike SDRAM where you could place it in just about an slot and get away with it. If this is your first time to building a machine, you probably picked the most hardest one as far as configuring is conserned as the terms that most slightly computer savy people are completely different, such as th Front side bus being 100 X 4 =400, instead of 66, 100, 133. You also must take more care when placing the CPU on the board and making sure that it is properly cooled, or it will fry. If you have any more questions, I would suggest posting them on the Motherboard forums as well as this one as most of us visit the motherboard/chipset forum more often.

    If it works for you then don't fix it.
  6. The CPU FSB is advertised as 400MHz. It is actually QDR (Quad Data Rate)x100. Which means that FOUR instructions are sent per clock cycle.
    The CPU multiplier uses the base cycle, so 1700MHz=17x100, even though Intel advertises a 400MHz FSB.

    Cast not thine pearls before the swine
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