iMac Memory Different Speeds?!?

[TaintedGG]

Hey Guys,
My parents are still running a 2010 iMac i5 I believe with merely 4gb (2 x 2gb pc3 10600) of ram. I see ram is always extremely high on usage but I can't justify spending $95 on 8gb of ram to boost it to 12gb.

So I've been searching online for second-hand memory and I'm thinking of just adding another 2 x 2gb sticks to double the memory. I found a good deal on 2 sticks, the only issue is they run at PC3 12800, above the speed of the other 2 sticks and above the rated speed for the iMac itself

My questions follow:
Will there be any issues with the sticks being different speeds?
and
Will there be any issue with the 2 new sticks being faster than the iMac's capability?

Thanks

 

[atomicWAR]

i would not do it. It may not work and even if it does it will likely be a performance penalty. I urge you to use the exact same make and model ram or replace all of it...or leave it alone all together.

 

[TaintedGG]

i would not do it. It may not work and even if it does it will likely be a performance penalty. I urge you to use the exact same make and model ram or replace all of it...or leave it alone all together.

Ok, thanks for your advice. The memory sold on eBay is said out have come out of a later generation mac book pro so I believe and both sets of sticks (currently owned and those sold on eBay) are Samsung manufactured so that wasn't of much concern. My hope was that maybe the higher rated speed memory would just not perform at it's rated speed but I am still unsure.
Thanks