Aspyr has released a free patch for Sid Meier's Civilization IV for Mac.
This will fully update any previous version of Civilization IV to version 1.61 Rev A. It is recommended for all users.
The update improves application performance on certain Macs (particularly G5s) that exhibited excessive CPU use in the original release. The game should no longer run dual CPUs to 100 per cent capacity.
The update also fixes numerous sound issues including missing sounds, stuttering, 3D sound positioning, and movie soundtracks.
The 40MB download is available here.