DDR2 800 5300u replaceable with DDR2 800 6400?

[fasted]

who makes the best memory sticks for gameing, i have a dell xps 420 (drzhdf1) ichanged the graphics card to nvidia 260, and am look to up grade memory dell said i have 2 sticks in there 1 ddr2 667, and 1 ddr2 800 and could add 2 more my first question is why did they mix i though they were suppose to be matched my second question is, i was looking to buy more memory i was looking at corsair ddr2 800 2gb memory sticks since i'm allowed up to 8 gig your suggestions and any help would be appreciated thank you

 

[Akashdeep]

Hard to say which one is best. You need to ensure the compatibility, reliability and waranty of the RAM that you will select for your Memory upgrade.

 

[damian86]

It is weird how they mixed them with different rams(as far as I understand) the 800 mhz could be running at 667 mhz.,I dont see the point in that unless he meant that your motherboard could come with 800 or 667 mhz rams

http://www.euro.dell.com/uk/en/dfh/Desktops/xpsdt_420/pd.aspx?refid=xpsdt_420&cs=ukdfh1&s=dfh

on tech specs says 667 / 800 MHz Dual Channel Dual DDR2 SDRAM, you should be fine getting 800 mhz sticks, normally they run at 667mhz by default, and then in BIOS you have to set them to 800.

BTW, you would be looking at PC2-6400 for ddr2 800