Please help me understand P4's and MB Speed

filter996 · 10-13-2005, 12:20 PM

Hey. So right now I have a P4 2.4 and 512MB PC2100 running on a MSI 845G Max MB. I'm really confused as to MB speeds.

P4's are supposed to have a busspeed of 400, 533, or higher. My memory is running at 266MHz, but my FSB is running at 133Mhz.

I think I understand memory. It doubles based upon your FSB speed. So since I have DDR266, my FSB is running at 133Mhz. If I had DDR333 my FSB would be running at 166Mhz. So if I had DDR400 my FSB would be running at 200 Mhz?

And how does the P4 say it runs at 400, 533, or higher? My board says it supports 400 or 533 so why does it only run at 133?

SHAWN · 10-13-2005, 12:40 PM

Your FSB for the chip will run at whatever its max speed is. Being that P4 fsb's are quad pumped if you have a chip that states 800fsb, its running at 200mhz x 4 = 800mhz. So it runs as if it was 800mhz but its only 2. 133mhz x 4 = 533mhz so your processor is running at 533 mhz.

PhillipBelcher · 10-13-2005, 12:49 PM

Well said Shawn

filter996 · 10-13-2005, 12:56 PM

Ahh. That's kinda what I thought it was, but you've made it so much clearer. Thank you. What about boards with a FSB of 166? Then the CPU would be running at 666, but I've never heard that advertised. This is where I started questioning myself. I guess it makes sense though. It may be, but that number doesn't make for good advertising.

SHAWN · 10-13-2005, 12:58 PM

There is no fsb of 666 as far as I know. However DDR Ram running at 166 is considered DDR333 or PC2700.

filter996 · 10-13-2005, 01:00 PM

Oh. So the RAM and FSB will move faster and in turn your computer, but not util DDR400 does the CPU get it's next jump to 800. Thanks. The Intel numbers are finally making sense to me. AMD is a whole other story. I have no idea how their Processor numbering works.

SHAWN · 10-13-2005, 01:07 PM

If you use DDR400 in a machine that has a 533 fsb, the Processor will be the bottleneck, however it will still run. You just wont get the most out of your RAM.

AMD is simple. Take a 3000+ processor. The chip runs at 1.8ghz but performes like a p4 3.0ghz. Imaging 10 bricks on one side that need to be moved to another. AMD would take 5 bricks 2 times but take more time to do it while the P4 would take 2 bricks 5 times but run really fast. As far as memory with AMD, on AMD motherboards they do not have a north bridge. The memory controller is on the chip. This allows a straight path from the processor to the RAM called Hyper Transport. Depending on the chip and the motherboard, it can run up to 2000mhz at this time. Now, the RAM is the bottleneck and there is plenty of room for RAM speed improvement in an AMD setup. I think that time is going to make the switch to AMD because they think about the future and not now. Not only that, AMD has had 64bit processors out alot longer than intel. Time can only tell us whats going to happen.

filter996 · 10-13-2005, 01:15 PM

So the AMD does more work per action so it can do the same amount of work slower.

How do they do this? Slower clock speed? Is this the idea that MAC uses cause they also run at slower speeds, but get alotta work done.

SHAWN · 10-13-2005, 01:22 PM

I dont know anything about MAC, its a new world to me so I cannot help you there. How they do it, I dont know. Its based on design I guess.

The General · 10-13-2005, 02:19 PM

i wouldnt want my FSB running at 666

it would be bound for failure.

or it would take over and kill me :-P

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