I have a couple Mac Pro’s at work (well, 3) that sit behind my desk doing render jobs, and running BOINC. They’re Mac Pro 1,1′s, so they date back to late 2006, but I’ve upgraded them with dual quad core processors, so they do okay. I’ve been keeping an eye out for ATI 5870′s to put in them for some GPU grunt, but they generally sell on eBay for $100/each. A couple weeks back, I saw someone was selling 2 for $75 total, and snagged them up. Once they got here, though, I realized an issue. They were made for some Dell, and have a weird bracket on them that you can see in the picture. It’s angled off to no doubt fit into some holder that those specific Dell’s have. Anyway, just thought I’d post that they DO work in the Mac Pro, you just have to grab a Dremel (or hacksaw) with a cutoff wheel, and after unscrewing the 12 or so screws that hold that bracket on, remove it, and cut the angled part off. Seriously, don’t try to put it off while it’s attached to the card… metal filings/dust are not great for electronics. The card then looks like a stock ATI reference card, and fits perfectly.
Make sure to throw the aluminum (aluminium) in the recycle bin. =)