MBPr 15 GPU temperatures?

[yliu]

I'm quite confused, as in iStat there are 2 temperature readings for the GPU, a 'GPU' and a GPU Diode'.


Whenever I do graphics intensive tasks, both GPU temperature values rise as the GT650 is being used. This makes me assume that the two temperature sensors are both on the dedicated GPU (GT650) and not the integrated GPU (HD4000).
What confuses me is that if I watch youtube videos, which still uses the HD4000, the temperature readings of 'GPU' and 'GPU Diode' still rises.

What does that mean? GT650 is turned on when I watch youtube?

BTW, is it normal for the GPU to heat up to ~55 Celsius while on youtube?

 

[lagisibuk]

Its normal.
I'm prefer using hd4000 for youtube and of course it will be decrease your gpu temp

 

[snaky69]

I'm quite confused, as in iStat there are 2 temperature readings for the GPU, a 'GPU' and a GPU Diode'.
View attachment 427498

Whenever I do graphics intensive tasks, both GPU temperature values rise as the GT650 is being used. This makes me assume that the two temperature sensors are both on the dedicated GPU (GT650) and not the integrated GPU (HD4000).
What confuses me is that if I watch youtube videos, which still uses the HD4000, the temperature readings of 'GPU' and 'GPU Diode' still rises.

What does that mean? GT650 is turned on when I watch youtube?

BTW, is it normal for the GPU to heat up to ~55 Celsius while on youtube?

The temps are for the gt650 only as the 4000HD is on the CPU's dye, thus temp is taken for it on the CPU.

 

[yliu]

The temps are for the gt650 only as the 4000HD is on the CPU's dye, thus temp is taken for it on the CPU.

Then why does the GPU temperature rise when I watch youtube?

 

[dusk007]

These both measure the 650M temps. GPU Diode is afaik the analog sensor.
They will always rise somewhat even when not in use because they are both on the same heatpipe. If the 650M is off, it still gets effectively heated by the CPU which in youtube load is probably at 70-90C.

Also have you checked if the 650M is actually off. Way too often it turns on because some app is running maybe in the background.

 

[rabidz7]

It is normal. If you are normal then re apply thermal paste to restrain the tempurtures.

 

[Queen6]

Then why does the GPU temperature rise when I watch youtube?

The cooling system is shared by both CPU & GPU therefore any radiated heat from the GPU is also passed to the GPU chip, hence the GPU temperature increases even when not in use. YouTube is predominately Flash based as a result the CPU on a Mac OS X system tends to work harder than on an equivalent PC the elevated CPU temperatures are simply transferred to the GPU by the cooling system (heat pipe).

Why do Mac portables function this way? Most likely this is the most efficient and cost effective route to cooling the systems CPU & discrete GPU chips. If You want more control over GPU switching or simply want to know which GPU is currently in use try gfxCardStatus this app will reveal the GPU in use, the application dependencies, and allow for manual switching of GPU`s.

Also don't get too preoccupied over the temperatures 55C is pretty low for the GT650M, it can be pushed as high as 100C, as can the CPU. Neither will overheat as both chips are capable of throttling; reducing core frequency, which reduces the power draw and temperature.

 

[yliu]

Thanks for the detailed answer!

Never thought of a shared cooling system between the CPU and GPU.

 

[Lord Xeb]

I'm quite confused, as in iStat there are 2 temperature readings for the GPU, a 'GPU' and a GPU Diode'.
View attachment 427498

Whenever I do graphics intensive tasks, both GPU temperature values rise as the GT650 is being used. This makes me assume that the two temperature sensors are both on the dedicated GPU (GT650) and not the integrated GPU (HD4000).
What confuses me is that if I watch youtube videos, which still uses the HD4000, the temperature readings of 'GPU' and 'GPU Diode' still rises.

What does that mean? GT650 is turned on when I watch youtube?

BTW, is it normal for the GPU to heat up to ~55 Celsius while on youtube?

55C is actaully not all that hot and I see these guys get close to 80-90C when under heavy load. It is perfectly normal.
GPU temp I believe is the temp taken from just outside the GPU die itself (either on the board, or on the PCB the silicon sits on). The GPU Diode is the diode within the GPU itself. It is normal for these to rise or even be off a bit (+/- 5C).