Adding a 667MHz RAM pair to a 533MHz RAM pair

[max789]

Hi all

I've a 1066MHz FSB Intel Core 2 Duo E6400 system with 1GB (512MB x 2) 533MHz DDR2 RAM. I'd like to add 1GB RAM and was going to get another pair of 512MB 533MHz DDR2 RAM. However, a friend has just offered me a pair of 512MB 667MHz DDR2 RAM cheaply.

I originally planned to stay with 533MHz RAM so as to keep a synchronous 1:1 FSB/RAM relationship for best performance.

Now, I wonder if mixing a pair of 512MB 533MHz DDR2 RAM with a pair of 512MB 667MHz DDR2 RAM will have a negative performance impact. I understand that such a combination runs at the lower 533MHz memory speed which is fine but since the 667MHz RAM will need to use a 5/4 divider and also has different timings, I'm a little concerned that performance will suffer compared to having identical 4x512MB 533MHz DDR2 RAM.

No overclocking is planned.

Your comments, please! Thanks.

 

[JustaGeek]

Both will have to work at 533MHz and same timings.

The faster memory should be able to run at the slower speed, but it is not guaranteed.

If you can, test it before you buy.

Good luck!

And welcome to AT forums!

 

[max789]

Thanks, JustaGeek.

The faster memory should be able to run at the slower speed, but it is not guaranteed.

Chances are very high though, aren't they (if the RAM sticks are of the same make/model)? Is it true that any difference in timings between the two RAM pairs will likely be accommodated with ease since there won't be any overclocking?

If you can, test it before you buy.

Is there a simple test for such purpose? Under CPU-Z SPD, the 533MHz RAM has two timings sets - 266 MHz and 200 MHz. Does it mean that, if I use CPU-Z on the 667MHz RAM and it has a 266MHz timings set (in addition to 333MHz timings) which is identical to that for the 533MHz RAM, things should be alright?

I notice that you use 6GB RAM with XP Home x86* and Vista Ultimate x64SP1* (dual boot, presumably). In view of the 32-bit address space limitations, how much RAM can you actually access under Win XP Home?

Thanks again.

 

[JustaGeek]

On one of my motherboards, the 667MHz memory would not work properly at 533MHz, so it is never guaranteed. And if you install them all together, they will all work at the same, lower speed (533, not 667 and 533 at the same time). The timings will either be set automatically by the motherboard, or you can do it manually, if the MB BIOS allows you to.

How to test it...? Ask your friend to let you install them, and you'll either pay him if they work, or return them to him if they don't.

Test them with Memtest86+ v. 2.01 and Orthos, and just in regular, everyday use.
http://forums.anandtech.com/me...=1901991&enterthread=y

XP Home, and all the other consumer versions of 32-bit Windows will address the maximum of 4GB of RAM minus all the PCI memory and Video memory. It will leave about 3GB of usable physical memory depending on the harware installed.

These will help you understand how it works:

http://h20331.www2.hp.com/Hpsu...M_w-Windows_08Ap07.pdf

http://www.dansdata.com/askdan00015.htm

 

[max789]

Thanks again, JustaGeek, for your detailed and helpful reply as well as useful pointers. Now I've a pretty good idea of the way forward.