I have an interesting observation (maybe).
Firestrike Ultimate Graphics test 1 hits the power limit easily so I tested this:
Test 1.)+37MHz core
-502MHz VRAM
127% PWR
GPU never dipped below 2000MHz and stayed at 2012MHz-2025MHz most of the time with occasional spikes to 2037MHz.
GPU-Z showed the card hitting the PWR limit and vREL at the same time.
Test 2.)+37MHz core
+0MHz VRAM
127% PWR
GPU was most of the time on 1987MHz-2000MHz with occasional dips to 1974MHz and spikes to 2012MHz.
GPU-Z showed the card hitting only the PWR limit
Test 3.)+37MHz core
+700MHz VRAM
127% PWR
GPU pretty much never goes above 1987MHz and usually stays at 1962MHz with dips even below that.
GPU-Z showed PWR limit.
In each of these tests, the GPU-Z showed 117.9% TDP max.
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Then I tried each test with 118% PWR and the core clocks went actually down in each test by 12-25MHz and now even the Test1 was entirely PWR limited.
GPU-Z showed max PWR to be 115.8%.
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Now with 100% PWR (only the test 3). The clocks were significantly lower. Most of the time in the low to mid 19xxMHz range with some dips below 1900MHz.
But GPU-Z showed the max PWR to be 106.1% TDP hmm...
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My conclusionThe PWR slider in the MSI Afterburner/Precision X definitely works. I am quite sure the PWR limit is 127% working as intended and I think that GPU-Z is spewing out incorrect PWR read outs.