what g.skill memory to use

[greglee]

I have 4 gb of memory in my computer with a 2.8 ghz i7 cpu and an ASUS p7p55d le mb. I want to upgrade to another 4gb of memory, however the G.Skill f3-12800cl7d-4gbrh is no longer available. I ordered 4gb of G.Skill f3-12800cl9d-4gbnq memory. Problem is only the "old" 4gb memory or the new 4gb of memory works. They will not work together to give me 8gb. If I return the new memory what is a compatible memory to use with the "old".?

[RamJam]

Try raising the DRAM Voltage by about .05 and also raise the Memory Controller Voltage about .1, if that is stable you can try lowering about .01 at a time

[Tradesman]

Might be able to mix them at CL 8 or CL9 and as Jammer said add a little voltage, maybe + .05 to the DRAM voltage and let us know how that goes