No random crash since the replacement of my video card a few months ago.
Based on past observations, here is what I believe happened :
1- For some reason, the external USB drive I was using for my monthly offline snapshot backup caused random shutdowns. Looking at the logs, it seems most crashes happened right after a Time Machine backup while the external drive was plugged in (although there was no error in the logs – simply a shutdown message).
2- I also experienced sudden shutdown while playing 3D games under bootcamp (Fallout and World of Warcraft). These were related to driver and heat issues.
3- These random crashes took a toll on the video card. Which in turn, added a stream of video glitches and more random shutdowns.
I believe this cycle happened about once a year, resulting in having to replace a faulty video card each time.
Conclusions ?
– Video cards for MacPro are sensitive to sudden shutdowns and may need to be regularly replaced (which is an issue for an aging 2008 MacPro).
– Gaming on a MacPro can be hazardous for the machine itself. Better set up a separate PC for games and dedicate the Mac for more serious tasks.