I'm not sure anyone would want to CPU mine.
Read:
http://http://bitcoinsbs.wordpress.com/2013/02/09/btc-mining-considerations/and
http://bitcoinsbs.wordpress.com/2013/06/27/quick-math-what-will-my-mining-rig-bring-in/CPU is roughly 100 times slower than GPU which is roughly 100 times slower than ASIC which is quickly becoming not enough.
Thus At the current rate
CPU makes about 10 MH/s
5 GH unit for $250 = 5,000,000 MH/s
With a network Hash rate just over 250 GH
and $100 BTC (round up)
The ASIC unit will make $216 a month
This means a CPU will make $0.000432 per month if it is doing 10 MH/s. Even if you could get it to run at 500 MH/s you would be looking at $0.0216 per month.
My 1.6 GH/s FPGA are earning me $0.02 per day and it's almost not worth it.
I do realize you said you're doing it for a hobby with CPU, but may be the last one. I have a feeling that because the CPU is so slow, you may not actually even be able to truely contribute and if you do find a hash it will be so stale that it will be discarded.
If you are interested in tuning, FPGA is still something that you can run fast enough to actually find hashes that can be submitted in a timely manner.
I'm actually not doing that badly. I don't mine 24/7, and I don't pay for the electricity (dad does, and he's OK with it).
Out of 150 shares submitted so far, I've only had 2 rejected (1 stale, one for unknown reasons).
I would like an FPGA board, but they're a little pricey, and the ones I have found which are cheap enough won't fit on my awkwardly designed motherboard (Supermicro X7DVL-3). I do have other reasons for wanting an FPGA board, though.
Find me a really cheap (in UK pounds) USB FPGA board, and I'll buy it. Good luck finding one...
Matthew:out