can memory speeds be mixed?

[meatloafsamwhich]

I currently have 2.5g of ram (two 1g sticks and two 256mb sticks). I intend to replace the 256mb modules with 1g sticks, bringing me up to 4g (the most my mobo can use).

The speed of my current two 1g sticks is 667mhz, though 800mhz will work with my computer.

If i install a pair of 800mhz ram will it function properly alongside a pair of 667mhz?
Does the faster ram need to be installed in the first slot to ensure the faster rate is used?
Should i just replace all the ram with 800mhz?

 

[a7xnck]

i don't think so? i think the slower ones will be left in dust and won't be recognized

 

[StrangleHold]

I currently have 2.5g of ram (two 1g sticks and two 256mb sticks). I intend to replace the 256mb modules with 1g sticks, bringing me up to 4g (the most my mobo can use).

The speed of my current two 1g sticks is 667mhz, though 800mhz will work with my computer.

If i install a pair of 800mhz ram will it function properly alongside a pair of 667mhz?
Does the faster ram need to be installed in the first slot to ensure the faster rate is used?
Should i just replace all the ram with 800mhz?

It will just down clock the 800 to 667. It will just auto clock it to the speed of the slower stick. Depending on your motherboard and what kind of memory the 667 is, you could go into the bios and fool with the Voltage and timing and see if you can get it back to 800. But it is always better to run memory thats all the same.