HSR stacking?

Hi everyone

Just checking, if I use these two items together will it give me TWO 20% chances every time I use a fire spell the recharge faster? or will it still just give me one 20% chance?

Kormab's Prism

Energy +12 (req. 9 Fire Magic)
Halves skill recharge of Fire Magic spells (Chance: 20%)
Health +30

Korshek's Scepter

Fire Dmg: 11-22 (req. 9 Fire Magic)
Halves skill recharge of Fire Magic spells (Chance: 20%)
Energy +5 (while Enchanted)

Thanks!

You'll have two times a 20% chance of HSR, or in other words a 36% chance in total. There is a slim 4% chance included that you even get a quarter skill recharge (although I am not sure if a -75% SR is still possible after the may 21 2010 update).
You find more info about this on the Wiki pages about so called "40/40" set if you are interested:
40/40 set on off. Wiki
Discussion Chance Calculation on off. Wiki
Discussion unoff. Wiki (Table for reference is simpler)

Thank you

Quarter recharge time was never possible, recharge reduction only stacks up to 50%.

So yes, you will have a 36% chance of half recharge time (of spells).


P.S. Please be aware that the 40/40 page linked above (and probably many other wiki pages) haven't been updated to incorporate the recent casting time modifiers nerf (May 21st 2010 update). The unofficial wiki page on 40/40 sets has been updated to reflect this. The update only affected the activation time modifiers though, so this update didn't affect the recharge time modifiers the OP asked about. I just wanted to give you complete information .

You will have 2 independent "rolls" for HCT to occur. That gives you a 36% chance of half recharge and a 4% chance of quarter recharge; BUT recharge is now capped at 50%, so your quarter recharge will be downgraded to half recharge. (Quarter recharge used to be possible before the cap was put in place.) The end result is that you get 40% chance of half recharge, but for different reasons than you'd think.

@ Dzjudz: You are right, my bad. I confused it with the quarter casting time.
@ Chthon: You are wrong. It's not 40%; it's 32% (to trigger once) plus 4% (trigger both) equaling 36% total.

Yes it's simple probability math confirming 36% is correct:
1 - (0.8 * 0.8) = 0,36 -> 36% chance.

Indeed, in theory you would have 32% chance of one mod working and 4% chance of both mods working. This is what used to happen with the HCT mods, before the May 21st update. This is also what used to happen and still happens with HSR mods, but those only ever stack up to 50% recharge, so effectively you have a 36% chance of HSR.

In short, with a 40/40 set:

before May 21st:
- 32% chance half cast time, 4% quarter cast time
- 36% chance half recharge time

since May 21st:
- 36% chance half cast time
- 36% chance half recharge time