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—for most trinkets and caster procs), or a relatively low proc chance with normalization based on weapon speed (PPM—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:
Windsong and Elemental Force Information | 2012-10-15 17:17 | 
Daxxarri
- Windsong is 2 Real PPM, and Elemental Force is 10 Real PPM.
- Come patch 5.1, Dancing Steel and Jade Spirit will be 2 Real PPM, River's Song will be 4 Real PPM, and Colossus will be 6 Real PPM
- Regardless of how you're attacking or healing, slow or fast, with DoTs or direct heals, whatever, you can expect to get the same proc frequency, on average.
- Dual wielding and having both weapons enchanted with the same enchant will double the frequency of procs that you get.
- This Real PPM is increased by your haste %. (The highest of your melee, ranged, or spell haste is chosen).
- Simple as that. Whether you're an Affliction Warlock dealing very frequent DoT ticks and
[Malefic Grasp] ticks, or a Holy Paladin casting purely Holy Light (Classic)s, or a Combat Rogue quickly attacking and using specials, or an Enhancement Shaman attacking with slow melee attacks and spells, or a Shadow Priest channeling 
[Mind Sear] on fifty Onyxian Whelps, you’ll get 2*Haste Windsong procs or 10*Haste Elemental Force procs per enchant per minute. - We're excited to see how this proc system works out. If it works well, we may start using it for more types of procs. Feedback about how it feels is most welcome.
Here are even more nitty gritty details, if you're interested:
- It can proc from any damage/healing event. It keeps track of the last time it had a chance to proc for that enchant.
- It calculates the difference in time since the last chance to proc. It uses that time to determine the chance for that event to trigger a proc.
- For example, if you have 22% Haste, it was 1.4sec since the last chance to proc, and you've got Windsong, then the chance to proc is 2(ppm) * 1.22(haste) * 1.4(time since last chance) / 60 (sec per min) = 5.693%.
- The 'time since the last chance to proc' is capped at 10sec, so that your first attack of a fight isn't a guaranteed proc.
In the same thread, a clarification was made about haste:
2012-10-15 22:44 | Zarhym
[Heroism] or 
[Bloodlust]), or even Mind-Numbing Poison will all affect it.In Patch 5.2, some functionality changes were made regarding haste:
RealPPM Functionality Changes | 2013-03-04 19:29 | Ghostcrawler
[Slice and Dice]) do not increase the frequency of RPPM procs. True haste boosts, such as Bloodlust or haste rating on gear will improve proc rate. We felt this change was necessary to balance proc rates among different specs.Patch changes[]
Patch 5.2.0 (2013-03-05): Haste rules changed.
Hotfix (2012-10-15): This new system, nicknamed Real PPM, aims to give the random nature of procs, the scaling with haste, and the ability for us to balance them assuming a standard proc frequency.
See also[]
External links[]
World of Warcraft Community Site Windsong and Elemental Force Information