How much power does the graphics card consume through the ATX connector
This is the third article dedicated to PCs. Other articles can be read here and here.
Tested graphics card
Model: Tested on ASUS Radeon RX 580 Dual OC 8GB
TDP 185W
1x 8-pin power connector (pinout shown below)
According to the above pinout, the current was measured at terminals 1-3 (+12V).
No-load, timebase 5ms
The highest recorded power Pmax=6.62 W
No-load, timebase 50ms
The highest recorded power Pmax=5.088 W
With load, 5ms time base
The highest recorded power Pmax=172.8 W
Average power Pavg=93.6W
With load, 50ms time base
The highest recorded power Pmax=177.6 W
Average power Pavg=103.2W
Summary
The test was carried out on a set with a motherboard with a PCI Express v3.0 connector, which is characterized by a maximum transferred power of 75 W. The tested graphics card has a power consumption of 185 W, simplifying the assumption that the ATX PCIe connector will have to download the missing approx. 110W
During the measurements, the highest (average) current that flowed through this connector was 9.2A, which gives 103.2 W at 12V.
Measurement of the current with an oscilloscope revealed that the nature of the current consumption of the graphics card is not constant, but pulsed. The value of this current under load oscillates between zero and 14.8 amps.
What happens when you put an EMI filter on the GPU power cord?
The solution did not work because it was very noisy. Every mouse movement was heard as a squeak coming from this filter.
More tests, this time with a new oscilloscope
Tests were performed with a 200MHz 1GSa/s oscilloscope. The voltage was measured on the ATX connector of the video card, value on the oscillogram it is displayed in the mode without the DC component (only ripple). The zero value for the current is at the height of the i[A] marker.
The ripple measured on the ATX connector is over 200mV at a current of 2.28A.
The above oscillogram shows the voltage boost by the power supply with increased power consumption by the graphics card.
