1600 ram is slower ram that can be overclocked to run at 1600 at a voltage of 1.65, the maximum you can do without permanently damaging your cpu.
The best way to see what your ram is doing is to run cpu-z.
91c is very hot, check that your cpu cooler is mounted well.
You could power down the PC and disconnect the power cord. Then push the cooler around gently to see if it wiggles. If it is not on solidly, then you need to remount it.
Look at the back of the motherboard to insure that all 4 pushpins are securely through and locked.
If you overclock by raising the BCLK, the ram speed will increase some . Don't sweat the ram speed or latency. The memory controller on the i7 cpu's is very good at feeding the cpu from ram. There is, at most, a 1-3% improvement in real application speed or FPS(vs. synthetic benchmarks) with faster ram or lower latencies. Not much worth it to me. I think it is much better to have the ram run at 1.5v which is the recommended value.
Just because you buy RAM rated to run at 1600mhz does not mean your system runs it at that speed by default. 1600mhz memory simply means that the memory is tested and guaranteed to work at that speed. This has nothing to do with the speed that your system runs the memory at by default.
You can change the voltage, the timings, and the divider to get the desired speed you want in the BIOS.
Download a little program called CPUz, or CPUID to find out all the details of your systems bus, memory, cpu speeds.
91 degrees Celsius that is too hot. Are you sure the heatsink is mounted correctly.
Last but not least, if the system SCREAMSSS, other than the CPU overheating problem, I would just leave it alone!
There is a problem though with your heatsink.
There is a setting in the BIOS that will allow you to set the clock for your RAM in relation to the FSB. It is called the FSB/DRAM Ratio. It usually defaults at 1:3.33 so you will get 1333Mhz. Set it to 1:4 and you will get the 1600Mhz that you want.
Randomkid and jitpublisher both had the best answers...but random is an apprentice, so i figured id help him out by giving him best answer.
Wow! Thanks for that... I wonder why I am not yet promoted to Regular when my points already exceeds 1500. But I saw some have exceeded 5000 points and remain to be regular when they should be veteran.