Yes you need to use BIOS F4 as Gigabyte disabled the Intel QST option in more recent BIOS versions for some reason.

You can download the HECI driver from Intel here

Yes thats not the MCH or ICH temperature. You can use BIOS F4 to check both MCH and ICH built-in DTS temperatures. Then you have to choose Intel QST for CPU Fan control If you want to check temperatures inside XP/Vista youll have to install the HECI driver. Intel QST will disable FSB overclocking an...

I also have a E4400 and the Tjmax is definately 85ºC. 34/35 at idle, open test bed using Intel box cooler. The revision is L2. M0 revision might be 100ºC A simple test I do is resume from S3. If temperatures are closer to ambient then Tjmax assumed is correct, if temperatures are 15ºC higher than...

Well it seems to be somewhere between 335~340MHz. Anything above is a no go.
E4400 L2 FSB800 CPU.

Yeah for me the issue is certainly related to the FSB.
Above a certain FSB speed S3 does not work, below that FSB speed everything is fine.
The multiplier or final CPU clock speed does not seem to matter much.

I cannot resume from S3 using XP while the FSB is OCed to 335MHz.
S3 resume is good up to 335MHz anything higher the system wont resume.
I thought it was something related to the E4400 CPU but people with E6600 are having the same problems.
Motherboard is P35-DS3, havent tested other OS

It is something else not the NB temperature, it is more like the system temperature.
I read somewhere that the sensor is installed at the end of the x16 PCI-E slot
MCH and ICH also have a DTS just like CPUs but you can only check the temperatures choosing Intel QST for smart fan control

You can only enable or disable "CPU Smart FAN Control".
As for the "CPU Smart FAN Mode" you can choose Auto, Voltage or PWM.

The fan control options are pretty scarce.

The board revision is 1.0,
A 4-pin fan is plugged into the CPU_FAN header
A 3-pin fan is connected into SYS_FAN2 header

BIOS controls both 4-pin headers.
Speedfan is able to control both as well.

I can control both 4-pin fans (CPU_FAN and SYS2_FAN)