Some new card stats:

MSI GTX 650 OC (2 SMX, 2 GB GDDR5 RAM):            1.95 kHash/s at -l K15x1 -C 1
Gigabyte GTX 650 Ti OC (4 SMX, 2 GB GDDR5 RAM)   2.20 kHash/s at -l K15x1 -C 1

the latter card costs marginally more and would have reserves for some LOOKUP_GAP fun (making this card last through NFactor 15 I hope).

Both cards were tested on Linux and have a factory overclock. Temperatures stay reasonable at 68C, unlike some low profile GT 640 (GK107) or single slot GT 630 cards (Fermi) I have tested (->99 deg C!)

The main drawback is that these are double slot cards. So you need risers to run 5 cards on a mobo. If you care more about densely packed hashing power, then get GTX 660 Ti or GTX 760 cards instead. These will cost twice as much however.

Today's improvements:

I fixed a serious problem causing validation errors in Kepler and Test (X-) kernels with -C 1 just now. I also redesigned some of the timer code for interactive mode. It will take less CPU now.

It may still make sense to increase the default batch size -b 1024 to something like -b 4096 or -b 8192 when running interactive mode with scrypt-jane. This costs a bit of display smoothness, but adds more hash/s.

Christian