I'm running on a 15" Retina MBP and have just been playing around with mining on it a little bit. I realize GPU mining is almost dead at the moment, but bear with me.
Overnight last night I was running the BitMinter Java client and getting around ~20Mh/s. I fired it up again this evening, and for some reason, am now only getting around 5Mh/s. I'm seeing the same rate on both the BitMinter java client as well as with cgminer. Nothing has changed on my system over the last day other than having to reboot it a few times for other reasons. Does anyone have any idea why my Mh/s output rate has fallen so much?
Did you had some update installed ? I recall I saw an update that had to do with the Nvidia driver.
In case you want to check, do the following:
Click on the Apple in the upper right corner and choose About this Mac. Click on more info... Click on system report. Click on Extension in Software. Sort this list on Last modified by clicking on the heading. Is there a new Nvidia driver listed ?