aymankoo

I had 1GB 512x512 533, I bought 2GB 667 but I only have 2 slot. I installed 2GB in one slot and 512 in anther slot. now I have 2.5GB, but I think the speed now is 533 not 667 as I know, so which is better in performance to put only 2GB 667 or 2.GB 667 and 512MB 533. ?!!

justpassingby

Hi aymankoo and welcome to TSF !

If you use unmatched ram sticks the speed will cap at the slowest timings and frequency, in your case 533Mhz and whatever timings the slowest stick uses at that speed.

The actual performances will depend on several factors.

First of all you should have bought 2 x 1GB 667Mhz instead of one 2GB stick to take advantage of the dual channel feature of modern motherboards. Using the 2GB 667Mhz stick in single channel could actually be slower than 2 x 512MB 533Mhz in dual channel.

Check the memory timings (the most important is the cas latency, mentioned first in the timings) : if the 533Mhz RAM works at 4-4-4-12 and the 667Mhz RAM works at 5-5-5-15 the 533 may give you better performances, even with less bandwidth.

If all sticks work at the same timings you won't notice much difference between 533 and 667Mhz memory. You'll probably never need more than 2GB of RAM with XP (I assume you use the 32bit version). If you want to check the max physical memory your computer ever needs then access the task manager at the end of the day (press ctrl+alt+del), go to the performances tab and check the peak value under commit charge at the bottom left. That's the max memory (virtual + RAM) that was ever used by the system since you turned the computer on. If it's less than 2GB you'll know you don't need more than 2GB of RAM.

It also depends on your CPU : you'll get better performances if you can achieve a 1:1 FSB:DRAM ratio, which means using 533Mhz RAM with an 1066Mhz FSB and 667Mhz RAM with a 1333Mhz FSB (DDR 2 533Mhz RAM works at a 266Mhz clock speed, which is the same clock speed a quad-pumped 1066Mhz BUS is based on => 1:1 ratio). If your FSB runs at 800Mhz or lower then the ratio doesn't matter much (unless you can overclock the 800Mhz FSB to 1066 but don't do that if you don't know anything about overclocking).

There are many memory benchmark tools available online, use Rightmark Memory Analyzer for instance. Go to the RAM performance tab to run a test then go to the results tab to save them as .bmp image files. That will tell you whether the 2 x 512MB of 533Mhz in dual channel perform better than a single stick of 667Mhz. Actual performances within a given program will then depend on whether the program needs more RAM or has enough with 1GB.