Force reboot when running C&C: RA3 on iMac 27" (mid-2011)

okay, got imac few days ago, , has been great.

purchased/downloaded command & conquer: red alert 3 mac game store. once installed , patched up, launched app , began play (after adjusting video/graphics settings in game, set ridiculously low , 800x600).

i've played game twice now, , each time - mid game - mac of sudden reboots. doesn't seem triggered particular action in game, randomly timed.

ideas?

p.s. video card amd radeon 6970 1gb

 

as follow-up, ran apple hardware test , checked out ok.

 

Forums Macs Desktops iMac

• iPhone
• Mac OS & System Software
• iPad
• Apple Watch
• Notebooks
• iTunes
• Apple ID
• iCloud
• Desktop Computers
• Apple Music
• Professional Applications
• iPod
• iWork
• Apple TV
• iLife
• Wireless