Such quirks can hit other DIY systems, as a couple of colleagues in our video department have found. One could not get the motherboard audio to work and finally purchased a USB audio adapter. He also had problems getting two monitors to work--he had to shut down and flip the rear power switch off and unplug the power cord from the wall, and then plug everything back in and start back up in order to see both displays. Another colleague's system would intermittently unmount FireWire drives, and his rear USB ports don't work at all.
Getting Blackmagic Design's Intensity Pro video editing card to work in the Bride of Frankenmac did not require any of the workarounds necessary for the ATI card. That's something of note for current Mac Pro users with PCI cards who want to continue using such cards inside a computer case instead of externally in a Thunderbolt expansion chassis with the upcoming Mac Pro.
It's worth mentioning that, unlike an Apple-built computer, our Bride of Frankenmac is not covered by an umbrella warranty. If the power supply conks out, we'll need to take that up with Antec. The same goes for all of the components. If anything breaks or stops working, it'll be up to us to deal with the individual component manufacturers.
Future OS X updates could also prove problematic to our custom setup. Apple, of course, does copious amounts of internal testing to make sure that software updates don't cause problems with its systems, but it could never test (or want to test) each update against every possible combination of components, especially components the company doesn't officially support. If you were to go down this unsanctioned path, whenever Apple released an OS update, you'd want to wait a few days before upgrading, then spend some time monitoring the forums to see if other folks are running into problems with their custom systems.
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