I5 6400 vs i5 6400T

[xdeath12x]

what is the difference between i5 6400 and i5 6400T (oem/tray)?

 

[DanielBen]

The t models are lower power versions this is done by lowering the clock speeds etc. in the case of the 6400 the t version has a lower base clock of 2.2GHz to the normal ones 2.7Ghz and also lower turbo boost speed of 2.8GHz to 3.3Ghz. So the t version is approx 15%-20% slower on benchmarks than the normal version. I have a i5-6600 myself which I deemed the best value processor at the time I purchased it which has a higher clock speed.