PLEASE HELP memory question - need to return today if I ordered wrong stick

Hey there, I'm an intermediate computer user with a question about a memory upgrade.

I just put a 1GB stick of PC3200 into my computer, because that's what some
utility told me to order. But when I took the old stick out, it said 266 Mhz on it, or PC 2100. My motherboard, an Micro Star MS-6533 (I know, I know, please don't laugh), indicated that it wants PC2100 or 2700 on their web page.

When I did the Linux Memtest, I was shocked to see that the FSB is set at 100 Mhz, requiring a 17x multiplier to get up to my 1.7 Ghz.

When I ran the utility from CPUID.com (CPU-Z I think) in XP, it said that my FSB is 100 Mhz, and the "rated bus" is 400 Mhz.

So, here's my question - Is my memory running in some sort of compatibility mode, and actually operating at 100 Mhz? Or Is it being quad-pumped and actually running at 400 Mhz?

I think I saw in CPU-Z the term "QDR" somewhere, which makes me think I might be OK...but I've never heard that term before, I've sort of stopped following hardware for awhile.

Your advice is GREATLY appreciated, because the memory has a 7 day return window, and I sure don't want to spend $50 to tank the performance of my PC.

Thanks,
Sasha
[email protected]



P.S. When I pulled the new stick and put one of the old sticks in, it still said it was running at 100 Mhz..which reassured me, but maybe the BIOS just got set to this compatibility mode.

 

welcome to hardwareforums,

Try benchmarking your computer with the old and then the new RAM, obviously you should score higher with the new ram

the only benchmark that i can think of off the top of my head for windows is 3DMark

 

Well, now to explain some very confusing math.

The Pentium 4 family introduced a quad-pumped FSB. It uses a base frequency (intially 100MHz) and quad-pumped that for 400MHz.

Next, you have DDR. This is an evolutionary step from SDR.
SDR transmits data at the rise of the clock. DDR transmits it at the rise and fall of the clock. At the same frequency DDR does twice the work, hence the title Double Data Rate.

Memory is like a tire speed rating, in that it indicates the maximum speed guaranteed. If you have a tire rated for 150MPH, it's going to work fine at 40MPH. The same concept is true of RAM.

By default, the motherboard will run the RAM in sync with the CPU's base clock. In your case this is 100MHz. DDR will be at 1600MHz, or DDR-200 (which runs at 100MHz).

 

Wow, thanks for you good explanation. I saw the letters "QDR" somewhere describing my memory, and I wondered if that meant "Quad Data Rate" or something similar.

Wow. I didn't even realize it, but yes my celeron has a P4 Willmette core - A "Celeron 4" as wikipedia calls it.


What really confused me, is when I went to CPU-Z and it said:

Bus Speed: 99.6 Mhz
Rated FSB: 398.4 Mhz

I didn't know if "Rated" meant what it was supposed to be running at, or what it really was because of some sort of multiplier. So I take it, if I have an early P4 cored chip, that it SHOULD be running at 100 Mhz FSB using 400 Mhz DDRAM, because it's quad pumped. Sweet.

The other thing I was confused about, was I thought that DOUBLE data rate ram should be running at 200 Mhz to make 400 Mhz. Thanks for clearing it up.