bad news: fan on my Mac Pro's old ATI HD 5870 video card started rattling uncontrollably. Cleaning it didn't fix the problem.
good news: I was able to flash an old Sapphire (ATI) 7950 with a UEFI-compatible BIOS, stick it in the Mac, and it works great.
bad news: took all day to work out how to flash it, AND fix the fans on the 7950,
Studio time: tomorrow.
Octodon is a nice general purpose instance.