NVIDIA 840M (laptop)
Did some overclocking just for fun and informational testing and here are the benchmark results:

OS: Windows 10 64bit
Driver: 355.60
oclHashcat v1.37

Default settings for WPA = 31,400 hashes per second
Default settings for MD5 = 790,000 hashes per second

+135 Mhz GPU Clock Offset = 35,100 hashes per second for WPA (11.78% performance increase over stock)
+135 Mhz GPU Clock Offset = 881,000 hashes per second for MD5 (11.39% performance increase over stock)

Tool used: EVGA Precision X 16 software utility. Raising the Mem Clock Offset will actually hinder performance so it's left alone. Most of us know already that unless you have adequate cooling, overclocking a laptop GPU is NOT recommended!

To put this into perspective, if it normally takes your word list 1 hour to complete, then:

10% increase = 6 minutes faster (54 minutes)
11% increase = 6.6 minutes faster
12% increase = 7.2 minutes faster

For 10 hours, a 12% increase in performance is about 1.5 hours shaved off of your time.
I was w8 for some bench for GT 840M.
I was comparing it shader units and speed to other cards and tought it would do 20.000 H/s
But 31,400 is great.
How long did you run WPA? Was it 10 minutes, 1 hour, or 1 day? How much heat did it produce?
Really? An 840M only does 790k MD5? My laptop has a 4 year old AMD 7690M XT and does twice that, and it was not expensive.
That means your laptop is from 2011. Strange since AMD 7690M XT is launched 2013
No? http://www.notebookcheck.net/AMD-Radeon-...662.0.html
But interestingly I only get 24.4k on WPA, 1394 MH/s on MD5. 

Actually Device Manager (among others) tells me I have an "AMD Radeon HD 6700 Series", but that changed after I installed modded drivers so I don't believe it. I bought the laptop in August 2012.
I think he meant md5crypt not MD5