When you start it up, a quick summary displays in your menu bar, updated approximately every 10 seconds:
The quick-status display indicates the highest temperature currently detected on the CPU sensor(s) and the highest RPMs currently of any of the fans (or the liquid cooling pump on liquid-cooled G5s). QuickFans will detect the fan speed and temperature for most software-exposed sensors on most Power Mac models, including and up to the Quad G5.
As a bonus, you can use QuickFans' internal PPCFanTool to also get this information from the command line. If you installed it to /Applications/QuickFans.app, go to Terminal.app and type /Applications/QuickFans.app/Contents/Resources/fans. To get a complete list of sensor data, type /Applications/QuickFans.app/Contents/Resources/fans -v. Here's what an example quad G5 might look like (this is an example, not intended as actual data):
PPCFanTool 1.0 Copyright ©2014 Cameron Kaiser. All rights reserved. Released under the Floodgap Free Software License. Drive Bay 37°C Backside 48°C Mem Controller 62°C Tunnel 45°C Tunnel Heatsink 42°C GPU 61°C CPU A Core 1 57°C CPU A Core 2 54°C CPU B Core 1 49°C CPU B Core 2 52°C Drive Bay 1000rpm Backside 1100rpm CPU A Intake 2089rpm CPU B Intake 2089rpm CPU A Exhaust 2185rpm CPU B Exhaust 2185rpm CPU A Pump 2583rpm Slots Intake 1560rpm
Please note that older G3 and G4
Macs may not have software-visible sensors and the tool will notify you
("No sensors") if no data is available. QuickFans does not yet
support accessing S.M.A.R.T. temperature data; if this is available from
your hard disk, Temperature Monitor can usually display this information.
QuickFans is freeware under the Floodgap Free Software License. It is only tested on 10.4.11, but should run on 10.5.8. This tool only functions with Power Macintoshes.