Bitcoin mining performance

I have 3 computers that currently have spare CPU/GPU capacity.  I decided to try out some bitcoin mining to see what kind of performance I can get.

The first computer I had available is a desktop.  It has a AMD Phenom(tm) 9750 Quad-Core Processor at 1.2Ghz and a GeForce GT 520.  It runs Ubuntu 12.04.  I couldn't find any miners in the Software Center.  I ended up downloading DiabloMiner.  DiabloMiner is a GPU miner written in Java.  This miner seemed to crash a lot, so I had to write the invocation with an infinite loop.  I got around 10-12 MHash/s.  What was interesting was that DiabloMiner also used 2 full CPU cores.  I couldn't find any evidence that it was using the CPU to actually perform mining.  It seems like the 2 CPU cores was some sort of "overhead".

The second computer I had available was a file server.  Due to hardware prices and availability, the file server is way too powerful.  It has a AMD FX(tm)-4100 Quad-Core Processor running at 3.6Ghz and a GeForce 210 GPU.  It runs Gentoo.  I could not get GPU mining to work.  I was able to install cgminer to use the CPU for mining.  One this hardware, I average 2.5-3MHash/s per core using the 4way algorithm.  I can get up to 9MHash/s out of the CPU, since I leave one core for everyone else.

The third computer is my VM server.  It has a AMD Phenom(tm) II X6 1090T Processor running at 3.2Ghz.  It has a Radeon HD 7870 GHz Edition GPU, but that is VGA-Passthrough'ed to a Windows VM.  It also has a GeForce GTS 250 for the Dom-0.  It runs Gentoo.  There are two Windows VM's and a Linux VM.  Each VM gets 2 cores.  The server also runs a bunch of other services like Apache, Samba and NFS.  The one Windows VM is my "gaming PC".  I could not get GPU mining to work on the GeForce GTS 250 card.  I could get cgminer working using the CPU, however.  I got around 3.5MHash/s per core using the 4way algorithm.  Depending on the time of day, I would use 2 or 3 cores for mining.  Using 2 cores for mining did NOT impact my gaming performance.

With the hardware that I had laying around, I achieved a max of around 27 MHash/s (as reported by the mining pool service that I use).  I would like to get at least one more GPU working.  Also, I would like cgminer to bump up to 5 cores on my VM server at night, but I have not found a way to change the number of cores cgminer uses dynamically.  So far, I kill the old instance then restart it with the new command line parameter.