Power delivery difference between PCI-E 1X, 4X, and 16x

Z

ZodaEX

Supreme [H]ardness
Joined
Sep 17, 2004
Messages
4,916
So I believe most of us here are familiar with the concept of a PCI-E 16x slot being capable of providing up to 75w of power through the slot. I've heard this over and over again for years.

But what about a PCI-E 1x slot? Can a PCI-E 1x slot also deliver 75W of power if I wanted to charge a laptop off of an expansion card off of the 1x slot that supports USB power delivery?

And what's the deal with the seldom talked about PCI-E 4x slot? Can a 4x slot be trusted to provide 75w of power as well?

I've read my motherboard's manual front to back, and it never brings this subject up.
 
Looks like power is on the small part of the edge connector.

1695684352037.png
 
I happen to have a copy of the PCI Express Card Electromechanical Specification, which says:

x1 standard height, full-length card is limited to a 10 W maximum power dissipation at initial power up. When the card is configured for high power, by default, it must not exceed 25 W maximum power dissipation or optionally it must not exceed 75 W maximum power dissipation. A x4/x8 or a x16 standard height or low profile card is limited to a 25 W maximum power dissipation at initial power up. When a card is configured for high power, it must not exceed 75 W maximum power dissipation.
Click to expand...

So it can be 75W for any slot, but 1x slots might be only 25W. Cards are supposed to query the slot for how much power they are allowed to draw.
 
The real question is why you're trying to charge a laptop off a PCIe card...
 
bwang said:
The real question is why you're trying to charge a laptop off a PCIe card...
Click to expand...
I mean, USB-C power delivery is a thing, and a thing that people actually use. Some would probably like the option of being able to feed a high-powered USB hub right off of their computer instead of needing to have an external hub with additional AC adapter. Most non-TB ports cap out at like 15W.

Not something I personally care to do, but i can definitely see the appeal of it.
 
vegeta535 said:
Get a wall charger then.
Click to expand...

Why would I get a wall charger when my current charger works just fine for my needs? I feel like you always try to make everything more complicated than it needs to be.
 
ZodaEX said:
Why would I get a wall charger when my current charger works just fine for my needs? I feel like you always try to make everything more complicated than it needs to be.
Click to expand...
You the one making it complicated. You said you were using a Blu-ray player to charge so assume you didn't have a wall charger.
 
pendragon1 said:
i think x1/4 slots are limited to 25w.
Click to expand...
Yes. If you want to put a PCIe x16 card (especially a GPU) on a PCIe 1x (or 4x) slot throught some converter, you need to add power (the missing 75W) to the converter. In principle there is a power connector on those converters.
 
ZodaEX said:
Why would I get a wall charger when my current charger works just fine for my needs? I feel like you always try to make everything more complicated than it needs to be.
Click to expand...
Because you're just playing with expensive stuff by avoiding using some more efficient cheap stuff.
 
You must log in or register to reply here.
Back
Top