Question about memory, 2 different types

[ViRaLRuSh]

I had a 512 corsair value stick, and just got a pny 512 stick for an upgrade. When I boot up, it says its not optimal unless its 2 of the same stick, but does this really matter? everything seems ok so far, no errors as of yet.

 

[ts3433]

It's not optimal, but you can probably run without problems.