Monday, August 22nd 2016

PCI-Express 4.0 Pushes 16 GT/s per Lane, 300W Slot Power

by
btarunr
 Discuss (75 Comments)
The PCI-Express gen 4.0 specification promises to deliver a huge leap in host bus bandwidth and power-delivery for add-on cards. According to its latest draft, the specification prescribes a bandwidth of 16 GT/s per lane, double that of the 8 GT/s of the current PCI-Express gen 3.0 specification. The 16 GT/s per lane bandwidth translates into 1.97 GB/s for x1 devices, 7.87 GB/s for x4, 15.75 GB/s for x8, and 31.5 GB/s for x16 devices.

More importantly, it prescribes a quadrupling of power-delivery from the slot. A PCIe gen 4.0 slot should be able to deliver 300W of power (against 75W from PCIe gen 3.0 slots). This should eventually eliminate the need for additional power connectors on graphics cards with power-draw under 300W, however, the change could be gradual, as graphics card designers could want to retain backwards-compatibility with older PCIe slots, and retain additional power connectors. The PCI-SIG, the special interest group behind PCIe, said that it would finalize the gen 4.0 specification by the end of 2016.
Source: Tom's Hardware

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75 Comments on PCI-Express 4.0 Pushes 16 GT/s per Lane, 300W Slot Power

#1
Nokiron
Finally some interesting progress with PCI-E. I'm not so sure what would change with this though.

Where do you draw the limit where the motherboard might be the bottleneck with GPUs powered by the slot?
Posted on Reply
#2
Mussels
Freshwater Moderator
300W slot power will be interesting, it'll make cards incompatible with old slots - and really heavy power draw from mobos.

I guess they'll need some kind of physical key system to prevent those cards going into older slots.
Posted on Reply
#3
btarunr
Editor & Senior Moderator
NokironFinally some interesting progress with PCI-E. I'm not so sure what would change with this though.

Where do you draw the limit where the motherboard might be the bottleneck with GPUs powered by the slot?
300W. The boards should have safety trips beyond that point, because you're delivering that power through traces, and not thick metal plugs. I imagine PCIe 4.0 motherboards with have PCIe power input connectors on the board.
Posted on Reply
#4
Frick
Fishfaced Nincompoop
btarunrI imagine PCIe 4.0 motherboards with have PCIe power input connectors on the board.
Aye, which makes it kinda moot IMO. The only benefit this has is cable management. And you break back backwards compatibility and looking at how little improvement there is in CPU performance it makes it downright bad.

Unless they make traces that really can do 300W, which is a lot.
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#5
Caring1
btarunr300W. The boards should have safety trips beyond that point, because you're delivering that power through traces, and not thick metal plugs. I imagine PCIe 4.0 motherboards with have PCIe power input connectors on the board.
I agree, they have already been doing similar with some boards by the addition of a Molex for extra power if needed.
Posted on Reply
#6
bonehead123
4x the power flowing through the slots, and you will also have 4x the heat produced too :)

So it looks like the mobo makers are really gonna have to step up their game in terms of trace and slot design, to accommodate this change, cause if they dont, there's gonna be hell to pay from mutli-mega billion $$ lawsuits over melted mobos and anything and everything attached to them, not to mention desks and houses burned down etc...........
Posted on Reply
#7
Nokiron
btarunr300W. The boards should have safety trips beyond that point, because you're delivering that power through traces, and not thick metal plugs. I imagine PCIe 4.0 motherboards with have PCIe power input connectors on the board.
Yeah, but that adds costs one way or another. This will inherently be more expensive than current solutions.
Posted on Reply
#8
JalleR
Maybe Motherboards will have Physical cables on the back with this new standard :)

Quad SLI/CF support.....

And that will mean a new PSU standard as well i guess...
Posted on Reply
#9
AlienIsGOD
Vanguard Beta Tester
Caring1I agree, they have already been doing similar with some boards by the addition of a Molex for extra power if needed.
My z77 ftw EVGA board has 4 pin molex on the board for that very reason
Posted on Reply
#10
Vayra86
I wonder why we would need this.
Posted on Reply
#11
Nokiron
AlienIsGODMy z77 ftw EVGA board has 4 pin molex on the board for that very reason
Yeah sure, but what with the budget-boards that suddenly need to be capable of 300W through the traces?
Posted on Reply
#12
lanlagger
"slot should be able to deliver 300W of power".. AMD right now:
Posted on Reply
#13
RejZoR
Ok, if 75W PCIe power delivery is such huge problem where people go batshit insane over RX480 issues, how are they planning to deliver PCB power traces to the PCIe slot without spontaneously combusting the board at 300W? Are they going to run external wires on the back of the boards? You can't make PCB traces that thick (well, you could, but it would be highly impractical), so, how?
Posted on Reply
#15
Mussels
Freshwater Moderator
ok external PCI-E cables that deliver 300W to an external box, THAT makes sense.

bring on the external GPU's that dont need their own PSU!
Posted on Reply
#16
TheLostSwede
News Editor
Mussels300W slot power will be interesting, it'll make cards incompatible with old slots - and really heavy power draw from mobos.

I guess they'll need some kind of physical key system to prevent those cards going into older slots.
Why would it make older card incompatible? The Voltage won't change, so there's nothing here to make older stuff incompatible, it's an increase in Amperage. A card will never draw more power than it was designed for, so this is a non-issue.

Time to learn some basics before making statements like that me thinks...
Posted on Reply
#17
TheLostSwede
News Editor
RejZoROk, if 75W PCIe power delivery is such huge problem where people go batshit insane over RX480 issues, how are they planning to deliver PCB power traces to the PCIe slot without spontaneously combusting the board at 300W? Are they going to run external wires on the back of the boards? You can't make PCB traces that thick (well, you could, but it would be highly impractical), so, how?
The same way some companies have been for years, 12V cables to somewhere close to the connectors on the motherboards. In other words, this won't help with the cable clutter...
Posted on Reply
#18
Mussels
Freshwater Moderator
TheLostSwedeWhy would it make older card incompatible? The Voltage won't change, so there's nothing here to make older stuff incompatible, it's an increase in Amperage. A card will never draw more power than it was designed for, so this is a non-issue.

Time to learn some basics before making statements like that me thinks...
not sure if i worded it badly, i meant new cards incompatible with older boards.
Posted on Reply
#19
Frick
Fishfaced Nincompoop
TheLostSwedeWhy would it make older card incompatible? The Voltage won't change, so there's nothing here to make older stuff incompatible, it's an increase in Amperage. A card will never draw more power than it was designed for, so this is a non-issue.

Time to learn some basics before making statements like that me thinks...
It makes new cards incompatible with old boards.
Posted on Reply
#20
Caring1
Musselsnot sure if i worded it badly, i meant new cards incompatible with older boards.
I understood that when I read it, but if the cards still have the 6 and 8 pin sockets they will be compatible.
Posted on Reply
#21
Mussels
Freshwater Moderator
Caring1I understood that when I read it, but if the cards still have the 6 and 8 pin sockets they will be compatible.
not if they do an RX480 and balance the draw incorrectly...
Posted on Reply
#22
Prima.Vera
Mussels300W slot power will be interesting, it'll make cards incompatible with old slots - and really heavy power draw from mobos.

I guess they'll need some kind of physical key system to prevent those cards going into older slots.
Shouldn't be the case since the Voltage will be the same. Is just the the slot would be able to deliver a lot more power now if required.
The question is, are the mobo manufactures still going to use the cheap shitty plastic to build the PCI-Express slots, or they will going to use other material, much more heat resistant?

Price increase seems like a no brainer....
Posted on Reply
#23
Ruru
S.T.A.R.S.
AlienIsGODMy z77 ftw EVGA board has 4 pin molex on the board for that very reason
I had a S939 board with a molex connector 10 years ago, so that truly isn't a new invention. I guess it was like for 7600GT SLI or something similar; cards which doesn't have a power connector, but two of them could be too much for a motherboard.
Posted on Reply
#24
matar
300w Slot power sweet no 6 pin or 8 pin power connecters = nice looking case no sticking out cables.
Posted on Reply
#25
iO
I really doubt we will see this in consumer boards. It looks more like an optional feature specifically aimed at server applications with new connectors and stuff..
Posted on Reply
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