Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
Mixing RAM can cause this problem in all computers. Mixing RAM doesn't always cause this problem, but it is one of the reasons why getting all the same RAM is ideal.

Nevertheless, I doubt you would ever be able to notice the speed difference in your applications even if you were trying to.
 
The iMac forum has an interesting thread about people adding 1600 MHz RAM that only runs at 1333 MHz.
https://forums.macrumors.com/threads/1508059/
Is this also an issue with the minis?

People get so caught up in numbers without truly understanding the ramifications. 1333mhz RAM vs 1600mhz will cause maybe a slow down of 1-2%. Maybe in high RAM Bandwidth scenarios you MIGHT see a loss of 5%, but in the end it will be negligible. Especially in an iMac which would have it's own dedicated VRAM, the system RAM plays a minimal role (only to feed the processor). In a Mini, where system RAM is also used as VRAM, there will at times be a bit greater impact, but in the end it wouldn't matter to 99% of the people in this world.

Here's a review Anandtech did comparing 1333mhz all the way to 2400mhz RAM and the impact to the system in Ivy Bridge (granted these are with desktop DIMM's, but beggers can't be choosy):

http://www.anandtech.com/show/6372/...333-to-ddr32400-on-ivy-bridge-igp-with-gskill

The biggest increase in gaming was 9% on the IGP with the smallest in crease around 4%. In any case, the difference didn't make the game anymore or less playable by running 1333 vs 1600. Again, an iMac wouldn't matter at all because, other than IGP, the differences were almost nill. Even the Mac Mini will barely matter (because it isn't like adding 1600mhz memory will suddenly make a game playable that wasn't before, most of the differences were within 1-5fps).
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.