Mixing RAM dimms?

[Yoshh]

I bought this DIMM and I was wondering if it's compatible with the ones I already have.

 

Is there any way to tweak the Command Rate and the CAS latency so that they'd work together? Do note that if they can't be run, I'll just use the HyperX and buy a second one later. Any ideas?

 

http://i.imgur.com/Cp0fpCH.png

 

Could it be that it's actually better to run the new 4GB alone rather than the 8GB but underclocked?

Edited October 30, 2015 by Yoshh

[HeyYou]

Stick it in,and try it out. Mainboard will run all ram at the same speed as the slowest ya got. If it can't figure it out, it simply won't boot.

[obobski]

+1 to what HeyYou said - it will likely boot at 666MHz CL9. As far as what's better (clock or capacity), favor capacity, especially when we're talking 4GB vs a larger capacity (assuming you have a 64-bit OS that can actually take advantage of >4GB). However it will also likely boot single channel, since you've got mismatched DIMMs (unless your board supports "uneven channels" (e.g. 2x2GB + 1x4GB in 3 slots for 2 channels, some boards really will do this). Ideal scenario is you have an even number of same-size DIMMs. Give this a gander wrt performance:

 

http://www.anandtech.com/show/6372/memory-performance-16gb-ddr31333-to-ddr32400-on-ivy-bridge-igp-with-gskill/8 (note that they're using an IGP for these)

 

Or if you prefer video form:

 

Or anecdotally: I upgraded from 1333 to 1866 and gained nothing in terms of frame-rate in benchmarks (like Crysis) or games (like Skyrim) [why did you upgrade to 1866 then? It was actually one of the cheapest 16GB kits at the time]

 

Or, tl;dr form: performance differences are very small.

[mark5916]

You may wanna be sure that each stick has the same cas latency, timings and voltage.

 

You can tweak these settings in the BIOS to make the two sticks match. You’d have mess around with it, and probably underclock at least one of your DIMMs in the process (if they have different speeds)

 

However, there is no guarantee it would work. !!!

As mixing only RAM speed with all the other specs the same, most probably your mobo will automatically underclock the faster, and you wouldn’t run into any problems.

 

And again there is no guarantee it will functioning, and at worse you may get a BSOD. (let's say if your DIMMS don’t like each other)