I did some benchmarking and tweaking of the ccminer code and was able to squeeze out a 5% hashrate increase mining HVC out of my 750 Ti rig (+800 khash/s per card). Not a big advancement but I think it's pretty good for a guy whose name is not Christian

I had initially removed support for all Compute versions except CC5.0, but I was able to get CC2.0+ compiled. Alas, I have no way to test whether this fork will work with CC3.5 and below, or on Windows for that matter. Therefore I can make no guarantee of your success if your rig uses either or both.

If you're brave, you can checkout my fork or view the full diff of changes..

Summary of changes:

* Compiled with CUDA 6 RC
* Made modest changes to hefty1 kernel. Honestly not sure these even made a difference; the original code from the C+C hash factory was already damn near perfect
* Changed code compilation
  * relocatable device code support
  * explicit linking via nvlink
* Removed maxrregcount to let compiler choose register count

My testbed specs:

OS	Ubuntu 13.10 x64, 3.13.6 kernel, NVIDIA 334.21 driver
CPU	Intel Pentium G3220 @ 3.00GHz (2 core)
Motherboard	MSI Z87-GD65
RAM	4GB DDR3 PC1333
GPUs	(6) PNY 750 Ti OC (stock, no mods, all 1x risers)
Risers	(6) 1x PCIe via USB 3.0 risers (slim)

And some performance metrics:

	Before	After
Hashrate/card	13400 khash/s	14200 khash/s
GPU RAM usage	186MiB	200MiB
GPU Temp (avg)	55C	56C

edited: more specs