ddr3 4gb ram compatible with ddr3 8gb ram?

[Delirior]

Hello,
I have my old ddr3 4gb (665mhz) , and I have 1 more slot for another stick , so Im wondering is 4gb ram compatible with 8gb ddr3 (1333mhz) or i should pick second stick of 4gb ddr3 ( 665)mhz?

 

[3hunna]

If it runs the 8gb ddr3 ram will lower it's speed from 1333mhz to 665mhz to keep up with it

 

[Delirior]

So should I go for it? Is mhz really important?

 

[Tradesman1]

Your old '665' DDR3 is prob it's true freq which means it's actually a data rate of 1333 since this is DDR (DOUBLE data rate) as DDR3 starts at a data rate of 800 (true freq 400). As far as mixing new with old it's a 50/50 crapshoot, there are no guarantees when mixing sticks, even if you get one identical to the old.