Upgrade Help - Mix memory

[solb8]

Hello.
My brother thinking about small upgrade.

his setup:
Geil 2GB DDR2 PC6400 800MHz Ultra
4-4-4-12 Metallic-Orange Aluminum Retail (2x1Gb)

GIGABYTE GA-P35-DS4 Silent Pipe
ATX,8xSATAII,GbLAN,2xPCI-E*16,ICH9R

q6600


The upgrade would be 2gb more ram, and a new gpu (gtx 460)

could i just buy 2gb of PC6400 800MHz and it will work together with the geil ?

like CORSAIR 2GB DDR2 XMS2 PC6400 800MHZ CL5 (2X1GB)
http://www.dustinhome.no/pd_5010092991.aspx

Its recomended to inst win7 on a system like this ?

 

[treefrog07]

The GEIL RAM is 4-4-4-? @2.0v
The CORSAIR is 5-5-5-18 @ 1.9V
Since the timings and voltages are different, you'll have to enter the BIOS and manually change the RAM latency settings to 5-5-5-18 and the voltage to 1.9V. You may also need to increase the Northbridge voltage by one "bump" or two since your are populating all the DIMMs.

If you do this, change the BIOS settings while the GEIL RAM is installed, but before you add the CORSAIR. Save and Exit the BIOS. Then disconnect the power cord, add the CORSAIR, then re-connect the power cord, and re-start the computer.