8 pin power

[Ebony Falcon]

Very confused, iv heard a lot that 8 pin vga cables can only plus 150w of power.

 

the amd 7900xtx hellhound and reference have 2x8 conections but both pull 440w+ when overclocked

(I know the slot can provide 75w but 375w is still under 440w) 

 

and then cpu 8 pin are ok up to 288w despite being basicaly the same cable ? 
 

would this card be safe with 2x8pin ? 
I dont understand 

 

update my cables are not daisy chained they are 8 to 8 

[mariushm]

The PCI-e organization that standardized the connectors decided to artificially limit the maximum power to 75 watts for the 6 pin connector and 150 watts for the 8 pin connector.

It's artificially limited in the sense that if a video card wants to call itself pci-e video card and put any kind of pci-e trademark, labels, advertising etc, then the video card is not supposed to take more than 150 watts or 75 watts through the connectors.

 

So a video card with two 8 pin connectors could in theory get 2 x 150 watts + 75 watts through the pci-e slot.

 

The video cards convert the incoming voltage (12v) to the voltages needed by the video card, like 0.6v .. 1.5v for the gpu chip, and maybe 0.8v to 1.5v for the ram chips, depending on the frequency they run at, and because there can be sudden variations in how much power the video card needs, it's possible for the card's power consumption to spike above the artificial limits for very brief periods of time.

 

The actual connectors, the pins/contacts, the wires, they all can actually handle a lot more power than those artificial limits of 75 watts and 150 watts, so from power supply and connectors and cables, it's safe for the video card to pull that much power for very short periods of time.

 

The actual pins are rated for at least 9A of current (it depends on how the pins are constructed on both plug and header) - EPS (cpu) cables have 4 pairs of 12v and ground, so the CPU can get 4 pairs x 9A x 12v = 336 watts at minimum.  Some motherboards and video cards rated for around 13A each.

 

The standard organization that standardized EPS and CPU (4 pin) connectors decided to artificially limit the current per pin to around 7A because their thinking is the pins are so close together on the motherboard there could be overheating issues if one pin fails (bad soldering joint, poor mating) and also to reduce the amount of heat produced inside the wires and along the wires, when the wires between the power supply and connector are so tightly bundled/grouped together (wires have resistance, so some energy will be lost on the wires themselves)

 

[Ebony Falcon]

13 minutes ago, mariushm said:

The PCI-e organization that standardized the connectors decided to artificially limit the maximum power to 75 watts for the 6 pin connector and 150 watts for the 8 pin connector.

It's artificially limited in the sense that if a video card wants to call itself pci-e video card and put any kind of pci-e trademark, labels, advertising etc, then the video card is not supposed to take more than 150 watts or 75 watts through the connectors.

 

So a video card with two 8 pin connectors could in theory get 2 x 150 watts + 75 watts through the pci-e slot.

 

The video cards convert the incoming voltage (12v) to the voltages needed by the video card, like 0.6v .. 1.5v for the gpu chip, and maybe 0.8v to 1.5v for the ram chips, depending on the frequency they run at, and because there can be sudden variations in how much power the video card needs, it's possible for the card's power consumption to spike above the artificial limits for very brief periods of time.

 

The actual connectors, the pins/contacts, the wires, they all can actually handle a lot more power than those artificial limits of 75 watts and 150 watts, so from power supply and connectors and cables, it's safe for the video card to pull that much power for very short periods of time.

 

The actual pins are rated for at least 9A of current (it depends on how the pins are constructed on both plug and header) - EPS (cpu) cables have 4 pairs of 12v and ground, so the CPU can get 4 pairs x 9A x 12v = 336 watts at minimum.  Some motherboards and video cards rated for around 13A each.

 

The standard organization that standardized EPS and CPU (4 pin) connectors decided to artificially limit the current per pin to around 7A because their thinking is the pins are so close together on the motherboard there could be overheating issues if one pin fails (bad soldering joint, poor mating) and also to reduce the amount of heat produced inside the wires and along the wires, when the wires between the power supply and connector are so tightly bundled/grouped together (wires have resistance, so some energy will be lost on the wires themselves)

 

Ok cool but that card can pull 440w constantly underload, is it safe ? 
 

[Somerandomtechyboi]

18 minutes ago, Ebony Falcon said:

Ok cool but that card can pull 440w constantly underload, is it safe ? 
 

I wouldnt worry about that, 150w is a bogus limit only for the shittiest of psus with the thinnest of cables

 

I wouldnt start worrying till were talking 600w+ and even then id have to check if the cables are even lukewarm cause as long as the cables arent even hot to the touch i wouldnt even bother worrying