Problems Mining: mbps is wrong, no blocks

[eric7]

I've tried mining with both BitMinter's official client and Diablo Miner. Both say I'm mining at ~27,700 mhash, which I don't think makes sense? I'm running a GeForce GTX 660M (#1) (2 CU, local work size of 256) on a brand new iMac i5 (16 gigs of RAM, does that matter?). I also haven't gotten any blocks yet, and my stats on BitMinter's website all say 0 for my worker.

Anybody ever seen anything like this? Seems very odd.

[btclvr]

With a switch from ATI to Nvidia, the new iMac takes a huge step back from the last two generations in terms of Mhash. See how your Nvidia GPU compares to ATI from the last two models.

https://en.bitcoin.it/wiki/Mining_hardware_comparison
http://en.wikipedia.org/wiki/IMac_(Intel-based)#Unibody_iMac

iMacs also use the lower clock speed mobile versions of GPUs that you would find in a laptop.