RAM speeds - Tilted Forum Project Discussion Community

Slavakion · 06-05-2004, 06:07 PM

So I know that when you get RAM, you're supposed to match the speed to that of your processor. It's something to do with the Front Side Bus, right? So how do you figure it out? I have SiSoft's Sandra, if that'll help at all.

Also, what's the "fudge factor?" I mean, how close do you have to be to the speed?

Thanks

Lasereth · 06-05-2004, 07:10 PM

You want your RAM to be the same speed as the FSB of your processor. If you can tell us which processor you have, that can narrow it down drastically.

Most newer processors take 1 of 3 types of RAM: PC2100, PC2700, or PC3200. PC2100 is 266 MHz. PC2700 is 333 MHz, and PC3200 is 400 MHz.

AMD lists the FSB of their Athlon XP processors as the aformentioned: 266 MHz, 333 MHz, and 400 MHz.

Intel lists the FSB of their processors with a higher core multiplier (basically for marketing). Pentium 4 processors have a FSB of 400 MHz (200 MHz Athlon XP), 533 MHz (266 MHz Athlon XP), and 800 MHz (400 MHz Athlon XP). Intel skipped the 333 MHz FSB and went straight from 266 MHz to 400 MHz FSB (in Athlon XP terms).

Maybe this will make it simpler:

AMD Athlon XP: (133x2) = 266 MHz FSB
AMD Athlon XP: (166x2) = 333 MHz FSB
AMD Athlon XP: (200x2) = 400 MHz FSB

Intel Pentium 4: (100x4) = 400 MHz FSB
Intel Pentium 4: (133x4) = 533 MHz FSB
Intel Pentium 4: (200x4) = 800 MHz FSB

The first number in the parenthesis is the true FSB of the processor. There's a core multiplier on all processors that basically "multiply" the FSB for marketing needs. AMD's multipler is 2. Intel's is 4. That's why an Intel Pentium 4 with 800 MHz FSB is the same FSB as an AMD Athlon XP 3200+ with 400 MHz FSB. Their true FSB is the same...200 MHz. The core multipliers are simply different.

So, if we can find out the FSB of your processor, then we can find out which speed RAM it takes. Just take the true FSB of the processor and multiply it by 2...that tells ya what speed of RAM you should use in your PC.

Furthermore, you *can* use different speeds of RAM with your processor, but it will slow down the system even if you have faster RAM than your processor. Putting 400 MHz RAM in a 333 MHz FSB processor system will slow it down. Having 333 MHz RAM in a 333 MHz FSB system will speed it up. Having slower RAM in a system will make it even worse off than that. Yes, it will work, but you should only do it temporarily until you can find the correct speed of RAM.

I hope I didn't confuse ya too much!

-Lasereth

Slavakion · 06-06-2004, 06:16 AM

Okay, at first I must have misread a lot of it, because I thought that my memory was not even on there. But I figured out that it's PC2700 SDRAM.

Thanks, Lasereth.

06-05-2004, 06:07 PM	#1 (permalink)
Slavakion Mjollnir Incarnate Location: Lost in thought	RAM speeds So I know that when you get RAM, you're supposed to match the speed to that of your processor. It's something to do with the Front Side Bus, right? So how do you figure it out? I have SiSoft's Sandra, if that'll help at all. Also, what's the "fudge factor?" I mean, how close do you have to be to the speed? Thanks

06-05-2004, 07:10 PM	#2 (permalink)
Lasereth Knight of the Old Republic Location: Winston-Salem, NC	You want your RAM to be the same speed as the FSB of your processor. If you can tell us which processor you have, that can narrow it down drastically. Most newer processors take 1 of 3 types of RAM: PC2100, PC2700, or PC3200. PC2100 is 266 MHz. PC2700 is 333 MHz, and PC3200 is 400 MHz. AMD lists the FSB of their Athlon XP processors as the aformentioned: 266 MHz, 333 MHz, and 400 MHz. Intel lists the FSB of their processors with a higher core multiplier (basically for marketing). Pentium 4 processors have a FSB of 400 MHz (200 MHz Athlon XP), 533 MHz (266 MHz Athlon XP), and 800 MHz (400 MHz Athlon XP). Intel skipped the 333 MHz FSB and went straight from 266 MHz to 400 MHz FSB (in Athlon XP terms). Maybe this will make it simpler: AMD Athlon XP: (133x2) = 266 MHz FSB AMD Athlon XP: (166x2) = 333 MHz FSB AMD Athlon XP: (200x2) = 400 MHz FSB Intel Pentium 4: (100x4) = 400 MHz FSB Intel Pentium 4: (133x4) = 533 MHz FSB Intel Pentium 4: (200x4) = 800 MHz FSB The first number in the parenthesis is the true FSB of the processor. There's a core multiplier on all processors that basically "multiply" the FSB for marketing needs. AMD's multipler is 2. Intel's is 4. That's why an Intel Pentium 4 with 800 MHz FSB is the same FSB as an AMD Athlon XP 3200+ with 400 MHz FSB. Their true FSB is the same...200 MHz. The core multipliers are simply different. So, if we can find out the FSB of your processor, then we can find out which speed RAM it takes. Just take the true FSB of the processor and multiply it by 2...that tells ya what speed of RAM you should use in your PC. Furthermore, you can use different speeds of RAM with your processor, but it will slow down the system even if you have faster RAM than your processor. Putting 400 MHz RAM in a 333 MHz FSB processor system will slow it down. Having 333 MHz RAM in a 333 MHz FSB system will speed it up. Having slower RAM in a system will make it even worse off than that. Yes, it will work, but you should only do it temporarily until you can find the correct speed of RAM. I hope I didn't confuse ya too much! -Lasereth __________________ "A Darwinian attacks his theory, seeking to find flaws. An ID believer defends his theory, seeking to conceal flaws." -Roger Ebert Last edited by Lasereth; 06-05-2004 at 07:14 PM..

06-06-2004, 06:16 AM	#3 (permalink)
Slavakion Mjollnir Incarnate Location: Lost in thought	Okay, at first I must have misread a lot of it, because I thought that my memory was not even on there. But I figured out that it's PC2700 SDRAM. Thanks, Lasereth.