I think what I'm asking is, is it worth doing, how bad is the default? I made a point to buy some 'faster RAM' for my PC before, and never bothers to adjust the BIOS.
The difference between 1600 11-11-11 and 1600-9-9-9 is probably 2-3% performance.
I typically hate fooling with memory timings. I hate lock-ups and I hate adjusting a setting and thinking it is stable only to adjust it 24 hours later. Since memory timings have several settings, I'd first just manually adjust for what they say they can do. If they don't, up voltage a notch and if they still don't set them back to default and enjoy the ram. Playing with timings is tedious work. 3 strikes your out rule works best, IMO.
this reply is accurate, however the modules themselves are rated for 9-9-9 @ 1600 operation, 1.5v.
the 11-11-11 is just for boards that you cant tweak dram timings on (oem systems come to mind) and the performance loss is as stated, 2-3% at most. if the oem system defaults to 1333, anyway; the xmp profile will likely have more agressive cas timings to make up for the frequency reduction.
dram timings can be very complex and tricky, but if you just mess with the basic cas settings such as CL latency, tRCD, tRP, and tRAS and maybe the command rate (1T or 2T), you would spare yourself from a lot of the headaches all those variables can bring.
(9-9-9-27-1T)
(CL, tRCD, tRP, tRAS, Command Rate)