Real PPM

Real PPM is a new method of handling procs on trinkets and enchants added in World of Warcraft: Mists of Pandaria. Rather than having a rather high proc chance with a significant internal cooldown (ICD&mdash;for most trinkets and caster procs), or a relatively low proc chance with normalization based on weapon speed (PPM&mdash;for melee weapon enchants), Real PPM aims to try something different - the random nature of procs scaling with haste, but still assuming a standard frequency.

From the official announcement post:

In the same thread, a clarification was made about haste:

In Patch 5.2, some functionality changes were made regarding haste: