Mixing 4GB DIMM's and 2GB DIMMS for 12 GIG (good or bad?)

Hello,

Firstly, it's worth saying that I have not been a 'performance' minded PC user for a long time but since my old CPU (Q6600) was getting long in the tooth I have upgraded have realised how out of date my PC knowledge is

I have built myself a new PC using a Gigabyte Z68AP-D3 Motherboard, an I5 2500k CPU and 8GB of Corsair Vengeance 8Gb DDR3 1600 (2x4Gb) CL8

However aside from playing The Old Republic and Battlefield 3 I do plan on using this PC to 'play with' a Virtual Machine (Running Ubuntu) so I thought it may be a good idea to get some more RAM (i know 8GB will be more than enough for most other things though)

As I have recently spent more than I care to admit to on this new machine i am trying to cut costs and am thinking rather than another 8GB of identical RAM I could drop in some Corsair Vengeance 4Gb DDR3 1600 (2x2Gb) CL9

Now back when I build my last machine mixing RAM was something that i would do without giving a second thought but it seems to be more relevant to performance in the newer chip set motherboards/CPU's and i am not sure it i would be making a mistake?

I thinking firstly will it work together?
Is it a good idea or will it effect performance in some way negatively?
Is there a 'real world' difference between CL8 and CL9 memory and does the differing size's of the DIMMS really matter?

TL DR Version - Can i mix

Eclipse Computers - Product Details

with

Eclipse Computers - Product Details

Or will it be rubbish and i should i get more of the 8GB stuff?

Mixing RAM is a bad idea because you can never be sure it will play nice. Given that, your memory isn't identical, but it's as close as can be without being identical. You shouldn't have any issues at all. I'm running 12 GB with a similar setup, except my sticks are identical...aside from capacities.

In terms of the timing from 8 to 9....absolutely zero real world difference. You'd have to run memory benchmarks and go into the gritty details to tell a difference.

Thanks for responding.

That's pretty much what I thought. I think it's probably going to be fine, my main concern was that the differing sizes would cause slowdown or something

I've run two VMs on 8 GB without issue as well. A have an XP system for old app usage, and a Server 2008 R2 box to play around with SharePoint. My home system has 12 GB simply because I had 4 extra GB sitting around, and at current prices, it wasn't worth reselling.