[Q] Ryzen and PCIe Lanes

[kfdsajgja]

Hi,

I wanna upgrade my rig with Ryzen, so I looked these components up:

Samsung SSD 960 EVO 250GB, M.2 (MZ-V6E250BW)
AMD Ryzen 5 1600X, 6x 3.60GHz, boxed ohne Kühler (YD160XBCAEWOF)
ASRock Fatal1ty X370 Gaming X (90-MXB5M0-A0UAYZ)

In addition I want to use this card:
ASUS XG-C100C, 1x 10GBase-T/5GBase-T/2.5GBase-T, PCIe 2.0 x4

Is the Ryzen plattform capable with installed GPU (GTX 1070 in my case) and NVME M.2 SSD (Samsung SSD 960 EVO) to support the NIC shown above with its PCIe 2.0 x4 interface? 

This hole PCIe Lane think is very unintuitive for me 

[The Sloth]

yes 

[themctipers]

yes, it should work

make sure to refer to your motherboard's manual to confirm which PCIe slots are using the chipset and which ones are using the CPU (you want the GPU to only be using the CPU to get 16x 3.0, and the networking card to use the chipset PCIe

[Glenwing]

1 minute ago, kfdsajgja said:

Hi,

I wanna upgrade my rig with Ryzen, so I looked these components up:

Samsung SSD 960 EVO 250GB, M.2 (MZ-V6E250BW)
AMD Ryzen 5 1600X, 6x 3.60GHz, boxed ohne Kühler (YD160XBCAEWOF)
ASRock Fatal1ty X370 Gaming X (90-MXB5M0-A0UAYZ)

In addition I want to use this card:
ASUS XG-C100C, 1x 10GBase-T/5GBase-T/2.5GBase-T, PCIe 2.0 x4

Is the Ryzen plattform capable with installed GPU (GTX 1070 in my case) and NVME M.2 SSD (Samsung SSD 960 EVO) to support the NIC shown above with its PCIe 2.0 x4 interface? 

This hole PCIe Lane think is very unintuitive for me 

PCIe lane assignment depends on which slot the device is plugged into. If you plug the network card into the second x16 slot, it will be using lanes from the CPU, which will drop the graphics card to x8.

 

Ryzen has 20 lanes, 4 will be used for the M.2 slot and 16 will be linked to the PCIe slots. The x1 slots use the auxiliary PCIe lanes from the motherboard chipset not the lanes from the CPU, so if you can find a PCIe x1 card your graphics card would be able to run at x16.

[knightslugger]

Yes. Remember you have TWO SETS of PCIe lanes: One from the CPU, and one from the chipset.

 

The CPU will give you 16 PCIe lanes

The Chipset will supply the rest that is generally reserved for other I/O such as SATA ports, Ethernet, Audio, USB, etc.

 

With what you have planned, you will have no trouble.

[knightslugger]

1 minute ago, Glenwing said:

Ryzen has 20 lanes

it has 16 friend, none of which are connected to the NGFF M.2 slot. those are wired to the Chipset.

[Glenwing]

3 minutes ago, knightslugger said:

it has 16 friend, none of which are connected to the NGFF M.2 slot. those are wired to the Chipset.

What I said is correct. 

[kfdsajgja]

So pls correct me if I am wrong now, but this is my understanding atm:

 

PCIe x16 Slot 1: GTX 1070

PCIe x16 Slot 2: NIC

M.2 Slot: NVME SSD

 

As far as I understand the manual of that MB, the x16 Slots will both run with x8 speed. This is because there are x16 for GPU, x4 for NVME and x4 for other I/O such as SATA ports, Ethernet, Audio, USB, etc.

 

So the only option here would be an upgrade to Threadripper if I want to run all components with full speed, isnt it?

[Brooksie359]

1 minute ago, kfdsajgja said:

So pls correct me if I am wrong now, but this is my understanding atm:

 

PCIe x16 Slot 1: GTX 1070

PCIe x16 Slot 2: NIC

M.2 Slot: NVME SSD

 

As far as I understand the manual of that MB, the x16 Slots will both run with x8 speed. This is because there are x16 for GPU, x4 for NVME and x4 for other I/O such as SATA ports, Ethernet, Audio, USB, etc.

 

So the only option here would be an upgrade to Threadripper if I want to run all components with full speed, isnt it?

All those components will run at full speed with those pcie lanes. 4x 3.0 is technically enough for may modern gpu so you will be more than fine with 8x

[Glenwing]

3 minutes ago, kfdsajgja said:

So pls correct me if I am wrong now, but this is my understanding atm:

 

PCIe x16 Slot 1: GTX 1070

PCIe x16 Slot 2: NIC

M.2 Slot: NVME SSD

 

As far as I understand the manual of that MB, the x16 Slots will both run with x8 speed. This is because there are x16 for GPU, x4 for NVME and x4 for other I/O such as SATA ports, Ethernet, Audio, USB, etc.

 

So the only option here would be an upgrade to Threadripper if I want to run all components with full speed, isnt it?

Yes. There are 20 lanes available (not counting the ones reserved for the CPU-chipset interconnect). On that board, 4 are reserved for the M.2 slot, and 16 are distributed between the two full-length PCIe slots. If only the upper one is populated, it will run at x16. If both slots are populated, they will both run at x8 each. As mentioned above though gaming performance isn't affected by PCIe 3.0 x8 vs x16.

[knightslugger]

That's just being ridiculous. Why include the 4 lanes that communicate to the chipset that are otherwise usable? unreal...

[Glenwing]

1 minute ago, knightslugger said:

That's just being ridiculous. Why include the 4 lanes that communicate to the chipset that are otherwise usable? unreal...

I didn't include them. Ryzen has 20 lanes NOT counting the ones reserved for the chipset. It has 24 total if you count those, which I don't.

[kfdsajgja]

2 minutes ago, Glenwing said:

Yes. There are 20 lanes available (not counting the ones reserved for the CPU-chipset interconnect). On that board, 4 are reserved for the M.2 slot, and 16 are distributed between the two full-length PCIe slots. If only the upper one is populated, it will run at x16. If both slots are populated, they will both run at x8 each. As mentioned above though gaming performance isn't affected by PCIe 3.0 x8 vs x16.

OK ty, but why do you write "On that board"? To be clear here, this PCIe Lane "problem" would be found on EVERY Ryzen board, because those CPUs just dont have more lanes, right?

 

Are there informative sources of that "x8 is fast enough for GPU" topic?

[Glenwing]

2 minutes ago, kfdsajgja said:

OK ty, but why do you write "On that board"? To be clear here, this PCIe Lane "problem" would be found on EVERY Ryzen board, because those CPUs just dont have more lanes, right?

 

Are there informative sources of that "x8 is fast enough for GPU" topic?

Yes, the lane count is the same on every board, but the board manufacturer can allocate them however they want. On that particular board (and most other boards), that's how the lanes provided by the CPU are set up.

 

PCIe gaming performance:

https://www.techpowerup.com/reviews/NVIDIA/GeForce_GTX_1080_PCI_Express_Scaling/5.html

[knightslugger]

2 minutes ago, Glenwing said:

I didn't include them. Ryzen has 20 lanes NOT counting the ones reserved for the chipset. It has 24 total if you count those, which I don't.

Maybe i have misunderstood something... I was under the impression that the 20 from the CPU did not include the oft forgotten chipset link. Time to review what i thought i knew...

[Glenwing]

3 minutes ago, knightslugger said:

I was under the impression that the 20 from the CPU did not include the oft forgotten chipset link.

That's what I said. 20 from the CPU, not including the chipset link. Board manufacturers have those 20 lanes to distribute to slots and devices. An additional 4 lanes are present (24 total) but reserved for the chipset so are ignored when discussing CPU PCIe lane assignments for your add-in devices, same way it's always been.

[kfdsajgja]

Ok thank you very much guys, that was very helpful for me (and many others I would assume)!

 

Those benchmarks are very distinct, so I probably would be fine running this config.

But the nerd inside cant stand the fact, that the GPU is not running at "full speed"

[mariushm]

Ryzen  has 24 pci-e lanes:

 

x16 : to graphics (depending on chipset can be split in 2x8)

x4 goes to m.2 (can also be split by MB makes in x2 + x1 + x1 or x2 + x2)

x4 goes to chipset

 

chipset is like a network switch, takes that x4 and creates multiple pci-e  2.0 lanes and other I/O lanes (which are like pci-e lanes) to which the sata and usb3 controllers and other things connect to ...

note that what you see below is in addition to a few usb 3 and sata ports already inside the processor itself

 

 

 

 

 

A 10 gbps ethernet card in theory can achieve ~ 1250 MB in either direction.

 

PCI-e v2.0 can do max 500 MB/s per lane and pci-e 3.0 can do around 970 MB/s per lane so in order to achieve that maximum speed, the card needs at least 3 pci-e v2.0 lanes or 2 pci-e v3.0 lanes.

Because there's no such thing as a pci-e 3.0 x2 slot (which would have been enough),and because the card may be installed in a pci-e v2.0 slot, they made the card with a pci-e x4 connection.

 

If you can accept the card not going over around 900-950 MB/s you can probably install it in a pci-e x1 slot on your motherboard (if the slot is designed that way.. must have the wall at the end removed)... it's perfectly legitimate to plug cards with wider edge into pci-e slots that are smaller, pci-e is designed ike that, to be moduar

 

If you have a board with B350 chipset, most iikely the second x16 slot on the board is ellectrically only pci-e v2.0 x4 lanes (2GB/s in either direction) coming from the chipset, but that's enough for your 10gbps card

[hb-hoss]

Hi Sorry for Opening this Old thread,

 

but If the Ryzen CPU gives his Lanes to SLI GPU on an AM4 Board 470x with 8x/8x and i change the CPU to Ryzen 3.Gen

 

and this CPU Supports maybe more then 8x/8x  maybe 16x/16X or 16x/8x

 

is it Possibel that this will work on the Old Board like it will Support PCI-e 4.0...???

 

Sorry for my english ;o)

[knightslugger]

3 minutes ago, hb-hoss said:

Hi Sorry for Opening this Old thread,

 

but If the Ryzen CPU gives his Lanes to SLI GPU on an AM4 Board 470x with 8x/8x and i change the CPU to Ryzen 3.Gen

 

and this CPU Supports maybe more then 8x/8x  maybe 16x/16X or 16x/8x

 

is it Possibel that this will work on the Old Board like it will Support PCI-e 4.0...???

 

Sorry for my english ;o)

Hard to say for certain. PCIe 4.0 isn't available yet. At any rate, PCIe 3.0 at 8x/8x may only slightly bottleneck, and may not be wired for true 8x/8x to the CPU. Some of the lanes might be passed through the chipset, it depends entirely on how the motherboard is wired. as it stands, SLI will only slightly bottleneck at 8x/8x on current PCIe 3.0 specification. I personally wouldn't worry about it unless you have a mission critical need for it, in which case i would use threadripper.

[mariushm]

It's unlikely there's gonna be more than 24 lanes directly from cpu (16 for video, 4 for m.2 , 4 to chipset) - they have to keep backwards compatibility with the socket, and I'm not even sure there's enough unused pins in the socket to allow for more pci-e lanes.

 

The new generation of Ryzen will support pci-e 4.0  but the motherboard also has to be made well enough to handle pci-e 4.0

One of the big deals about pci-e 4 is the limitation when it comes to maximum distance between pci-e controller (inside the cpu) and the device at the other end - basically, from what I heard, the maximum distance between socket and pci-e slot must be below 165 mm  (or is it between chips, including distance from slot to gpu chip, i don't know)

 

So even if an existing motherboard would be validated and tested and proven to work at pci-e 4.0 speeds, it may be that only the first pci-e x16 slot would run at pci-e 4.0 - because the second slot is quite further from the cpu socket, it may be the case that when you put two cards, the connection will automatically fall back to pci-e 3.0

 

The workaround for that is to use re-driver chips, chips that amplify and retransmit the signals, and those would allow longer distances between slots and cpu socket - but obviously you can't retrofit existing motherboards to add those chips.

 

What we could eventually experience, maybe towards the end of 2019, start of 2020 when more pci-e 4 starts to show up,  we may have middle to high end ATX motherboards with 3-4 pci-e slots, that add pci-e "splitters" which convert the x16 lanes from the cpu into  x8 + x4 + x4 , or x4+x4+x4+x4  , I think that's possible with the Ryzen processors, provided additional chips are used on the motherboard