On a laptop with integrated (Intel HD5500) and discrete (AMD Radeon R7 M265) the applications startup using the integrated graphics by default. setting the variable DRI_PRIME=1 causes the applications to use the discrete graphics instead.
"glmark2" runs on the integrated graphics vs "DRI_PRIME=1 glmark2" runs on the discrete graphics.
"chromium-browser" runs on the integrated graphics vs "DRI_PRIME=1 chromium-browser" runs on the discrete graphics.
You can also force the use of radeon graphics by the use of a grub flag.
ati - Very Low Temperature Reading for graphics driver using lm-sensors - Ask Ubuntu:
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