[SOLVED] Can PCIe 4.0 work with 2.0?

[Jasio_]

Can PCIe 4.0 work with 2.0?

 

[rgd1101]

what pcie 4.0 device?

 

[drea.drechsler]

Can PCIe 4.0 work with 2.0?

Short answer is PCIe is both forwards and backwards compatible so it should. That means you could plug a PCIe 4.0 device in a PCIe 2.0 socket - or PCIe 2.0 device in PCIe 4.0 socket - and it will work at the highest version and bandwidth (lanes) that BOTH support.

 

[rgd1101]

on page. yes. there power and other compatible issue.

 

[drea.drechsler]

on page. yes. there power and other compatible issue.

PCIe power (the small part of the connector close to the I/O plate) is limited...to 15W I believe?...but that limitation is overcome by the 6 or 8 pin "EPS" connectors on GPU's that need more than that. The 15W limitation is pretty much as 'standard' as the rest of the PCIe spec, I'm pretty sure.

The connectors, however, are covered in the EPS+12V specification, if I'm not mistaken?

Compatibilty wise...well...as long as mfr's play fast and loose with their compliance to specifications in attempts to gain marketplace advantage there will always be compatibility issues. Famously, for instance, AMD broke the PCIe spec by pulling way over the 15W limit on their first RX480 reference boards. I think they had to rush out a BIOS update to keep people from toasting their motherboards.

 

[rgd1101]

pcie is 75W. and old motherboard with pcie 2.0 might not supply that enough

 

[drea.drechsler]

pcie is 75W. and old motherboard with pcie 2.0 might not supply that enough

ahhh....you're right...6.5A is not 15W! Never trust headmath. But my understanding is/was that PCIe 1.0/1.1/2.0 all have the limitation of 6.5A (75W at 12v) in the slot. I've never heard for sure but has PCIe 3 and up increased that? I assumed not, as the safe amperage it can pass is constrained by the contacts which has not changed.

But that said, of course some motherboard mfr's may very easily have skimped on older PCIe 1.0/1.1/2.0 motherboards and not laid in the copper for 6.5A as they should have. As I said, mfr's do crazy things when they try to game spec compliance to gain advantage.

 

[Jasio_]

what pcie 4.0 device?

Graphic card

 

[SkyNetRising]

PCIe power (the small part of the connector close to the I/O plate) is limited...to 15W I believe?...but that limitation is overcome by the 6 or 8 pin "EPS" connectors on GPU's that need more than that. The 15W limitation is pretty much as 'standard' as the rest of the PCIe spec, I'm pretty sure.

The connectors, however, are covered in the EPS+12V specification, if I'm not mistaken?

Completely mistaken.
EPS +12V is for cpu power. It has nothing to do with PCIE power.

PCIE slot provides 75W.
6pin PCIE power connection provides 75W.
8pin PCIE power provides 150W.

 

[drea.drechsler]

Completely mistaken.
EPS +12V is for cpu power. It has nothing to do with PCIE power.

PCIE slot provides 75W.
6pin PCIE power connection provides 75W.
8pin PCIE power provides 150W.

So I mis-applied the EPS acronym, which I did have a question about it when I wrote it, for the GPU power...you know what I'm talking about. And at any rate, your pedantry has nothing to do with whether PCIe is or is not forward/backward compatible.

 

[rgd1101]

Graphic card

so the XT 5xxx ? what motherboard do you have? system spec?