Well, recently I began tinkering around in Apple's CHUD Tools, that I downloaded to look around in. One application that happened to come to my attention was one called 'Reggie SE'. This application apparently lets you, among other things, manipulate the various registers that are present in your processor. Three of these registers that were named THRM1, THRM2, and THRM3 especially caught my eye.
A quick look online at various documents regarding the PowerPC 750, and more specifically the 750GX, showed me that these involve the G3's thermal sensor. I happened to come upon a small note in the various sections talking about the G3's Thermal Assist Unit (TAU). This particular note said that enabling bit 31 (V-bit) in both the THRM1 and 2 registers, and bit 31 (E-bit) in the THRM3 register would enable the G3's thermal sensor.
Sadly, I have no way of looking on a G3 running OS 9 because of the lack of a utility such as 'Reggie SE'. I wanted to see if maybe the reason that no temperature monitors for OS X could detect the G3's thermal sensor was because maybe OS X no longer enabled it. So, I needed to see if OS 9 did.
Luckily, I know enough to know that I really don't know what I'm talking about. Of course, if it were this easy, someone would have already done it. What are you opinions on this?