Speedfan

[Soviet_Genius]

Speedfan gives me four readings, but how do I know which one is which? They are labeled Temp1 (Asus F8000), Temp2 (Asus F8000), Temp3 (Asus F8000), and Core (AMD K8). I think the one labeled "core" is the video card because it gives me the same reading as rivatuner.

[Broni]

Basically, SpeedFan reads whatever your BIOS says, so to really know, which temp is which, you have to go to BIOS, and see what's there.

http://www.almico.com/sffaq.php

Which temperature is which?
There are several ways to label available readings (temperatures, voltages, fan speeds). The first source should be the BIOS. Enter BIOS at boot, write down labels and readings and compare them to those reported by SpeedFan. You can use manufacturer's custom hardware monitors to match readings too. SpeedFan strictly adheres to available datasheets for each sensor chip. Please remember that hardware monitors chips have some pins (small connectors) that should be connected to some additional hardware (temperature probes, thermistors or thermocouples) in order to be able to read temperatures. Only a few hardware monitor chips do label their connectors with "CPU", "System" and the like. Most of them use labels like "Temp1", "Local" or "Remote". Hardware manufacturers connect available pins to different temperature sensors basically according to the physical placement of components on the motherboard. This means that the same chip, an ITE IT8712F, for example, might be connected to a sensor diode measuring CPU temperature on Temp2 and, on a different hardware, it might be connected on Temp1. If you have a "Local" sensor and a "Remote" labeled one, this usually means that "Local" is the temperature of the monitor chip itself and "Remote" is the temperature read from a "remote" probe. When you have properly identified which temperature sensor is which, try to lower the speed of each fan and look at reported speed and temperatures. This way you can match PWM controls (speeds) with fans. Please, note that if you do not allow SpeedFan to change any fan speed and set all the speeds too low, then SpeedFan won't be able to avoid overheating.

[Soviet_Genius]

I went through all the possible screens in BIOS and couldn't find the temperatures anywhere. This is what I'm guessing, based on the temperatures themselves:

Temp1 (46C) is the processor
Temp2 (-128C) is the disabled onboard video
Temp3 (39C) is the hard drive
Core (54C) is the video card

[Calum]

Sounds right to me.
However, Temp2 is probably not be an actual reading, sometimes Speedfan does that.

[Broni]

Temp2 is probably not be an actual reading, sometimes Speedfan does that

With those "weird" temps, most likely non-existing sensor.