New MOBO runs hotter?

I assume you mean your CPU temps if not please ignore the rest. If you are talking about idle temps it could be the power saving settings in the bios if its load temps its more likely to do with the thermal paste or the fan installation. Also can you tell if the fan is spinning at the correct/same speed? Also what CPU, Motherboard and cooler do you have & what overclock and temps are you getting?

Hi Simon

Yes sorry, I am talking about CPU temps.

I'm not sure what settings in the bios are the power saving settings, do you know what they're normally called?

The thermal paste and fan installation has been re-done and checked a couple of times - all is good.

The fan is spinning just as it was before, tried it with and without the fan controller (i.e. from the mobo and from the fan controller)

it's an X2 5000+ CPU with an Arctic Cooling Freezer 7 Pro rev 2 cooler. I've OC'd it to only 3.0Ghz (it can get to 3.2) and at Idle i'm seeing around 40 Degrees...but on my old mobo I was seeing 33ish.

Rich

Do you have cool and quiet enabled in the bios and did you before?

Before, the CPU fan was connected to a fan controller, so cool n quiet wouldn't have made any difference (right?).

I've tried my new setup with and without the fan controller.

I just thought are you looking at the CPU sensor or the core temps? If you are looking at the CPU then its quite likely that 1 or both boards just had an inaccurate sensor.