I found a factory referb Asus KFSN4-DRE on eBay for $39 for 2 8356 Opterons and 4 gig of mem I had laying around due to my inability to straighten some CPU socket pins on a Arima.
After discovering that Boinc 7.0.xx and Ubuntu 12.04 have some problems I decided to try something different. Having a long and distant past with FreeBSD using it for routers, firewalls, web and ftp servers both personal use and professional I decided to give PC-BSD a try. PC-BSD is basically FreeBSD with a GUI install front end and a app package system that makes installing desktop stuff easy. While I did like the GUI install I found problems with the configuration programs. I ended up doing it the old fashion way and hand editing the config files. But it is FreeBSD and the same docs will be relevant.
Boinc WUs run under Linux emulation on *BSD. I had heard years ago that Linux apps ran from almost as fast to faster so I was curious how they would do. BoincTasks show the CPU % for the PC-BSD WUs 90-98% whereas my other dual 8356 running Ubuntu shows 99%+. Yet Top shows mostly 100% for the WUs.
So it has run long enough to have some WUs validate.
Project -- PC-BSD ----- Ubuntu
C4CW - 3.96-4.00 ~ 3.48-3.52
GFAM - 3.85-4.28 ~ 4.69-5.04
FAAH - 4.46-7.73 ~ 6.17-7.74
HCC - 1.75-2.13 ~ 1.66-1.95
Both 64 bit. PC-BSD installs Boinc 6.4.5 and Ubuntu had 7.0.24. All samples were 4 WUs or more.
What I take from this is if you want to install FreeNAS(FreeBSD based) on a storage array or build a BSD firewall, server, router and wonder how Boinc will do it will do fine. SO FAR it seems FAAH and GFAM like BSD a little better but the samples are not that big, some of the above time crunching I was doing other things that might have increased the CPU time and all WUs are not the same. I have a second dual 8356 running Ubuntu 10.04 desktop and it's numbers compare with the above.
At this time the Boinc version in the FreeBSD ports tree is 7.0.25.
In a few days I may install FreeBSD and try compiling Boinc. With PC-BSD I installed everything and I want to try a minimal install next.
Just discovered that I seem to have gotten the 32bit Boinc.