AMD cards actual power consumption/Kill a watt accuracy?

undertaker2k8

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This is actually a dual question: how far off is AMD's wattman reported power consumption from actuals (I understand NV is pretty accurate). Also how accurate are the kill-a-watt P3 meters over 1 KW?

Reason I ask are the following observations (using a Corsair RMX 850W for the 3090 and the EVGA 650 B5 cascaded for all other cards):

3090 Only (tuned for 305w) mining : 510 W power draw on the meter (200W system and miscellaneous device consumption like a router and external HDD connected to it, not unexpected)

3090+3080 (tuned for 225w) mining: 770 W power draw on the meter

3090+3080+6700xt (tuned for 97w)+ 6600xt (tuned for 60w) - 975 W power on the meter

3090+3080+6700xt (tuned for 97w)+ 6600xt (tuned for 60w)+ 6700xt (tuned for 97w, final one I added yesterday) - 1140W! on the meter

Not sure if the final reading is accurate, obviously PSU efficiency and loss play a factor here but both PSUs should be 87% or above across the load spectrum. The Sapphire 6700 xt card I added yesterday actually seems to be marginally better than the first Gigabyte in terms of power consumption reported in wattman by 1-2 w so I doubt that is an issue. Thoughts?
 
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Andrew_Carr

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Have you looked at the efficiency curve of your PSU? Depending on how you're moving through it it's probably changing the efficiency by a few percent as you add more load.
 

undertaker2k8

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Have you looked at the efficiency curve of your PSU? Depending on how you're moving through it it's probably changing the efficiency by a few percent as you add more load.
I believe it's 87% or above for 20-100% load but will double check. My rough calculations are the load on the EVGA 650 is in the 500-520w (225W 3080 + 60W 6600xt + 2X 110W pessimistic actual usage from the 6700xts ?) range, which should be fine for long term use.
 

undertaker2k8

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This is the only place I saw a review with efficiency by load measurements for this family of PSU (for the 550 w but the 650 w should be very similar):

https://hexus.net/tech/reviews/psu/144901-evga-550-b5-psu-550w/?page=3

Even assuming the efficiency falls by 3%, that should be an extra 15 w of loss, not 70-80 w, hence the question of the accuracy of the P3 over 1 KW since I think it's max power rating is close to 1.8 KW (15A/@120V).
 

undertaker2k8

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Alright, well they claim accuracy to within 0.2% for the meter. The closest thing to an efficiency curve I can find for the EVGA PSU is here https://hexus.net/tech/news/psu/140414-evga-launches-affordable-b5-series-80-plus-bronze-psus/

Looks like about a 5-6% drop from max efficiency to the efficiency at max load.
I have to pay PGE so every watt counts lol, even with solar offsetting a bunch. Though I think I am not gonna try and down tune the 6700xts below 97w for now (separate conversation), too many headaches. May try a higher rated PSU if I feel like it somewhere down the line. Thanks for the responses!
 
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