8x in 16x pci-e?

[Renaldsq]

Hi,

So, can you put pci-e 2.0 8x graphics card in 3.0 x16 slot? it is possible?

[Eigenvektor]

Yes, you can. It will simply only use x8. PCIe is backwards and forwards compatible in terms of version, so a 2.0 card will work in a 3.0 slot and vice-versa.

 

~edit: You can also plug a x16 card into an (open-ended) x8 slot, it'll simply be limited to x8 in this case.

[Renaldsq]

15 minutes ago, Eigenvektor said:

Yes, you can. It will simply only use x8. PCIe is backwards and forwards compatible in terms of version, so a 2.0 card will work in a 3.0 slot and vice-versa.

 

~edit: You can also plug a x16 card into an (open-ended) x8 slot, it'll simply be limited to x8 in this case.

ohh, i got it. but what x8 and x16 does mean?

[Kilrah]

The number of parallel PCIe lanes that are used/connected.

[Renaldsq]

i have last one question, what does 65W on processor or GPU means? Or is it just using watts per hour?

[DoctorNick]

53 minutes ago, Eigenvektor said:

Yes, you can. It will simply only use x8. PCIe is backwards and forwards compatible in terms of version, so a 2.0 card will work in a 3.0 slot and vice-versa.

 

~edit: You can also plug a x16 card into an (open-ended) x8 slot, it'll simply be limited to x8 in this case.

Actually if you where to run a x8 2.0 card in a x16 3.0 slot it would only take up x4 3.0, because 3.0 has double the bandwidth of 2.0. (of system bandwidth that is. Not phycally slot size ofc)

[Eigenvektor]

21 minutes ago, Renaldsq said:

i have last one question, what does 65W on processor or GPU means? Or is it just using watts per hour?

You're probably referring to the TDP, which stands for Thermal Design Power. As the word "thermal" suggests, this is about cooling and not power draw. It is a measure of how much cooling is needed to run the CPU/GPU at its base clock (though the exact meaning of TDP varies by manufacturer)

 

So it has basically nothing to do with the amount of power the CPU/GPU is going to use.

[mariushm]

No, it's more like a "class" , a rating of how much heat the heatsink and cooler must be capable of handling.

 

A 65w TDP processor may consume up to 80-100 watts for short periods of time, and may consume less than 10 watts when you're in windows just typing a document or watching a Youtube video.

The basic idea is that a cooler designed to handle 65w worth of heat will be good enough to keep the cpu cool even if it consumes more than 65w for brief moments of time (because it takes some amount of time for all that metal in the cooler to heat up, and then the fans can blow air and cool the metal as soon as the cpu stops consuming so much power)

 

Video cards are limited in how much power they can consume by the connectors.

In order to be called a pci-e video card, the video card must not consume more than 75w from the pci-e slot, more than 75w from any pci-e 6 pin connector or more than 150 watts from a 8 pin connector.

It doesn't mean that the video card will consume that much, just that it can consume UP TO that much.

 

For example, a card like GTX 1060 consumes up to 125 watts.  This means the card could use a single 6 pin connector (75w from slot + 75w from pci-e 6pin = 150 watts).

But the video card maker may use a 8 pin connector and take around 100 watts from the 8 pin connector and only 25w from the slot, and still have around 50 watts of reserves on the 8 pin connector and 50w in the slot in case user wants to overclock.

 

[Eigenvektor]

2 minutes ago, DoctorNick said:

Actually if you where to run a x8 2.0 card in a x16 3.0 slot it would only take up x4 3.0, because 3.0 has double the bandwidth of 2.0. (of system bandwidth that is. Not phycally slot size ofc)

A PCIe 2.0 x8 card has as much bandwidth as PCIe 3.0 x4, true. But it is still going to require/use 8 lanes, because it is physically connected to 8 lanes of PCIe 3.0, which then simply run at PCIe 2.0 speeds.

[DoctorNick]

Just now, Eigenvektor said:

A PCIe 2.0 x8 card has as much bandwidth as PCIe 3.0 x4, true. But it is still going to require/use 8 lanes, because it is physically connected to 8 lanes of PCIe 3.0, which then simply run at PCIe 2.0 speeds.

Exactly what I said just using other words

[mariushm]

1 minute ago, DoctorNick said:

Actually if you where to run a x8 2.0 card in a x16 3.0 slot it would only take up x4 3.0, because 3.0 has double the bandwidth of 2.0.

No, that's not true.

 

If the device (the video card) is pci-e 2.0, then the motherboard will downgrade the connection to pci-e 2.0 mode... an old video card can not magically understand a more modern version of the pci-e protocol.

 

The motherboard makes 16 pci-e lanes available, the device you plug in the slot can use as many as it wants. It could be 8 pci-e lanes, it could be 4, it could be even 1 pci-e lanes - you can plug a wireless pci-e x1 network card in a pci-e x16 slot if you want to, nobody's gonna stop you, and it will work perfectly fine.

 

The other way works as well.  You can plug a pci-e x16 card into a pci-e x8  or a pci-e x4 slot or even a pci-e x1 slot - as long as there's no wall at the back of the connector and no components in the path, the card will work in the slot, with part of its edge connector just hanging in the air.

 

The motherboard offers the number of pci-e lanes ( 16, 8, 4 or 1) and the device takes as many as it wants. In theory, the device must not refuse to work even if the slot has only one pci-e lane, but some devices (for example some sas/sata controllers or 40/100 gbps network cards) may refuse to work unless there's at least 4 pci-e lanes in the slot,

 

 

[DoctorNick]

4 minutes ago, mariushm said:

No, that's not true.

 

If the device (the video card) is pci-e 2.0, then the motherboard will downgrade the connection to pci-e 2.0 mode... an old video card can not magically understand a more modern version of the pci-e protocol.

 

The motherboard makes 16 pci-e lanes available, the device you plug in the slot can use as many as it wants. It could be 8 pci-e lanes, it could be 4, it could be even 1 pci-e lanes - you can plug a wireless pci-e x1 network card in a pci-e x16 slot if you want to, nobody's gonna stop you, and it will work perfectly fine.

 

The other way works as well.  You can plug a pci-e x16 card into a pci-e x8  or a pci-e x4 slot or even a pci-e x1 slot - as long as there's no wall at the back of the connector and no components in the path, the card will work in the slot, with part of its edge connector just hanging in the air.

 

The motherboard offers the number of pci-e lanes ( 16, 8, 4 or 1) and the device takes as many as it wants. In theory, the device must not refuse to work even if the slot has only one pci-e lane, but some devices (for example some sas/sata controllers or 40/100 gbps network cards) may refuse to work unless there's at least 4 pci-e lanes in the slot,

 

 

Let me try again. As an example a system has a total of 24 PCI-E 3.0 lanes. You plug in a 8x 2.0 card. Yes the card will run 8x. 2.0, but it will only take 4x of 24x of PCI-E 3.0 lanes

[Eigenvektor]

3 minutes ago, DoctorNick said:

Let me try again. As an example a system has a total of 24 PCI-E 3.0 lanes. You plug in a 8x 2.0 card. Yes the card will run 8x. 2.0, but it will only take 4x of 24x of PCI-E 3.0 lanes

No. It will still take up 8 lanes. So it will not leave more lanes for other purposes.

[mariushm]

7 minutes ago, DoctorNick said:

Let me try again. As an example a system has a total of 24 PCI-E 3.0 lanes. You plug in a 8x 2.0 card. Yes the card will run 8x. 2.0, but it will only take 4x of 24x of PCI-E 3.0 lanes

No, it will take 8 of the pci-e 3.0 lanes. the pci-e controller will downgrade those 8 lanes to pci-e 2.0  (500 MB/s vs ~985 MB/s per lane) and those 8 lanes will be connected to the video card.  You will get in total a bandwidth of 8 x 500 MB/s = 4 GB/s

 

pci-e 2.0 uses 8:10 encoding meaning for every 8 bit of information, 2 bits are error correction. pci-e 3.0 switches to 128:130 encoding , so instead of 20% of bandwidth being error correction and shit, pci-e 3.0 uses less than 2% of bandwidth for error correction.

 

The pci-e 2.0 video card can't suddenly understand how to encode and decode 128:130 encoding, it will keep using 8:10 encoding, and it's the controller's (motherboard) job to go down to 2.0 mode and talk to the device.

[Renaldsq]

Give me short answer, will it work or no?

[mariushm]

Yes it will work.

[shaz2sxy]

2 minutes ago, Renaldsq said:

Give me short answer, will it work or no?

Yes

[Kilrah]

Yes. You got that answer as the first word of the first reply.

[Renaldsq]

1 minute ago, Kilrah said:

Yes. You got that answer as the first word of the first reply.

xDD

[DoctorNick]

41 minutes ago, Eigenvektor said:

No. It will still take up 8 lanes. So it will not leave more lanes for other purposes.

Oh yes you are true right. Guess I need something to drink. Getting hot in here. Summer is comming  

Sorry for the confusion boys.