Low CAS Latency Or High Data Rates?
Neither. DDR3-2400 CAS 12, for example, has 50 percent more bandwidth than DDR3-1600 CAS 8, but both of them take the same amount of time to initiate a transfer. Large packets of data will speed up nicely with the added bandwidth, but many of the programs we use show no appreciable difference, though you will see performance improvements when using the higher data rate DRAM in things like multi-tasking, working with video, imaging, CAD, VMs or applications that use large data sets.
Want to get ahead of the game? Look for a good combination of the two, like this:
1600/7 1866/8 2133/9 2400/10 2666/11 2800/12
Each of the above progressions will provide slightly better performance. Also, there are times when a lower data rate DRAM with tight timings will outperform one with a higher data rate. For example, DRAM that runs at 1866/8 will outperform 2133/10 or 11 DRAM.
You can find a tighter CL at those frequencies. Both Corsair and G.Skill have CL9 sets in 2400, and you can find a few sets of 2133 with a CL of 8.
I tend to stay away from any DRAM at 1333/10 or 11, 1600/10, 1866/11 and up and so on. With those timings and with pricing as it is, you can often find a lower data rate set of DRAM that will outperform higher data rate DRAM for the same price.
