Surface Pro 3 throttling

The TDP and total power is about the same for the i5. I measured it with the intel power gadget. I was getting very similar numbers for an uncooled i5. The one difference is that I don't have anything that pushes my graphics to 11.4W or the i5 doesn't go that high.

That could be because the HD 5000 has 40 execution units compared to the HD 4400's 20, but it could also be because we are using different stress tests. Could you try furmark to keep it consistent? And if gpu-z doesn't say 11.4W, what does it say?

The TDP and total power is about the same for the i5. I measured it with the intel power gadget. I was getting very similar numbers for an uncooled i5. The one difference is that I don't have anything that pushes my graphics to 11.4W or the i5 doesn't go that high.

You might have found a difference between the i5 and i7. In my tests the body gets warm triggering the throttling when the CPU gets to around 80C. I can get the CPU higher if I drop the body temperature, maybe around 90. I wonder if they changed T_body_high in the time between the release of the i5 and i7 or if they simply have a different value. I have some thermometers and even a $15k thermal camera at work. Maybe next weekend I'll play around a bit.

Also can you find out what the max TDP that is being used is before the throttling happens? My i7 supposedly has a max TDP of 25Watts but before throttling according to the Intel power gadget it is using 16.97. Also according to gpu-z the Intel HD 5000 is using 11.4watts. With throttling the TDP drops to 10ish watts and the GPU to around 6.4 watts, and with my USB fan preventing throttling my TDP sits at 15.9Watts and the GPU at 9.9 Watts. I wonder if the i5 uses less than that or if they're the same.

You might have found a difference between the i5 and i7. In my tests the body gets warm triggering the throttling when the CPU gets to around 80C. I can get the CPU higher if I drop the body temperature, maybe around 90. I wonder if they changed T_body_high in the time between the release of the i5 and i7 or if they simply have a different value. I have some thermometers and even a $15k thermal camera at work. Maybe next weekend I'll play around a bit.

I plan on doing more tests about the "T_high" once I get a hold of a laser thermometer. According to the internal sensors on the processor and GPU, they both hit 90C before the throttling starts which is pretty high considering the TJ max is 100C and not 105C like my ivy bridge laptop. I also placed my hand over the CPU as soon as the throttling get started and it is almost to the point it hurts my hands, but if I had a thermometer I could actualize that into a number. When I'm using my USB fan workaround the GPS stays at 90C but the CPU registers as 78C, as well as the metal seeming cooler to the touch. However that could just be because the fan is blowing on my hands as well,  so again a thermometer would help for better tests.