RAM Questions..

Hey guys,

just recently upgraded my mid-2009 macbook pro ram from 4GB to 8GB, it ran (2x) 2GB 1066 mhz DDR3 ram sticks that are now out of the machine. I also have a mid 2011 iMac that is only running 4GB of RAM at the moment and has 2 empty spots. Now that one runs 1333 mhz DDR3 sticks. Basically my question would be wether or not i can take my old macbook pro ram and put those in my iMac slots giving me 8GB of RAM in both machines.. Advice would be much appreciated.

Thanks!

No. The modules from your 2009 MBP are the wrong speed and specs. Go to OWC or Crucial and get the correct modules for your iMac.

Just postulating that if the RAM sticks are of the correct size and voltage. Putting slower RAM in the system, despite having more RAM will decrease performance. Also if you have say a single 1600Mhz RAM stick and you have a 1333mhz RAM stick. If you put them both in the system (not recommended, but often can work) the faster RAM stick will drop down to the speed of the slowest stick.

Often then not, if both RAM modules (sticks as I tend to call them) are of the same type being say 204-pin DDR3 SO-DIMM and 1.35-1.5volts. are the same and you want to put slower RAM in, it should work. But it will make the whole system slower despite the added amount of RAM. The issue with going with faster RAM is that the BIOS (or the computers hardware subsystem) may not see the RAM and if it does, it may make the RAM run at a lower spec'd speed.

Now you should never mix RAM, I don't even like to mix brands. Due to timing, voltage, speed, and even smell issues, it can make a system unstable. I recommend you to follow chscag's advice. Its the best solution and will give the best stability.