PCIe lanes and Ryzen APU

[FAHEYGF87]

I'm working on a parts list for a high speed PCIe storage solution, and I can't seem to wrap my head around PCIe lanes with onboard graphics.

 

PCIe lanes are the link between a CPU and PCIe device(GPU), right?

 

If the GPU is already on the CPU, does that take any PCIe lanes?

 

Also, are PCIe lanes CPU or chipset specific?

[SignatureSigner]

A cpu has a certain number of 'lanes' when you have a gpu plugged in its going to use bandwidth. Some cpus like the EPYC and Threadrippers have TONS of lanes. For example, on some MOBOS when you put in a NVMe ssd it might disable another SSD slot because there is only so much bandwidth or 'lanes'. I most likely did a bad job explaining that but i tried. 

 

This might help

https://forums.tomshardware.com/threads/ryzen-g-series-processors-pcie-lanes-question.3551521/

[Electronics Wizardy]

How high speed? What drives and network cards are you using?

 

The apu's only have a x8 link from the cpu instead of a x16, so normally the top slot will run at x8 max, and the second one won't function.

[Moonzy]

Just now, Electronics Wizardy said:

The apu's only have a x8 link from the cpu instead of a x16

dont ryzen cpu have 20 lanes?

but i guess x4 is dedicated to NVME

 

8 minutes ago, FAHEYGF87 said:

If the GPU is already on the CPU, does that take any PCIe lanes?

for APU, yes

[Electronics Wizardy]

Just now, Moonzy said:

dont ryzen cpu have 20 lanes?

but i guess x4 is dedicated to NVME

There is a total or 24 lanes, with almost all boards using 4 for the chipset, 4 for the top m.2 drive, and the last 16 for the gpu(or other pcie) in the top pcie slot, can be split with the second slot in a supported system). The apus have a total of 16 lanes, so that x16 for gpus/slots is now a x8. How this is used really depends on the board.

[FAHEYGF87]

20 minutes ago, Electronics Wizardy said:

There is a total or 24 lanes, with almost all boards using 4 for the chipset, 4 for the top m.2 drive, and the last 16 for the gpu(or other pcie) in the top pcie slot, can be split with the second slot in a supported system). The apus have a total of 16 lanes, so that x16 for gpus/slots is now a x8. How this is used really depends on the board.

The plan at the moment:

 

24 total lanes

 

16x PCIe NVME raid card - 8 remaining

 

4x M.2 boot drive - 4 remaining 

-----------------------------------------------------

 

Would i be better off getting a 1x PCIe card like this, with something like a R5 2600, or just a R5 3400g? 

 

 

[Electronics Wizardy]

1 minute ago, FAHEYGF87 said:

The plan at the moment:

 

24 total lanes

 

16x PCIe NVME raid card - 8 remaining

 

4x M.2 boot drive - 4 remaining 

-----------------------------------------------------

 

Would i be better off getting a 1x PCIe card like this, with something like a R5 2600, or just a R5 3400g? 

 

 

What board are you using? You need to make sure your board lets you use the lanes like that.

 

What programs are you using on this system?

 

Id probalby just get a i3 10100 here, faster cpu, and igpu included still.

 

The apus only have a x8 from the cpu in the main slots, so that pcie nvme card won't work right, or at a lower speed. What care are you using? Does it need birfucation support?

[Steace]

Sorry for reviving the post... Morning...

 

For the last part of your question about specifics.

The CPU have it's own lanes, the chipset(s) add more lanes.

On AM5 you can also have 2 chipsets that add even more lanes.

Chipsets lanes are slower because they communicate with the chipsets then the CPU.

The extra chipset on AM5 is going through the first one then the CPU so even slower than "normal" chipset lanes.

Also, if what's connecting to those lanes are close to the CPU, you'll have less latency since they need less time to travel. That the reason why the faster m.2 connector is always very close to the CPU and also why the faster pcie4 16x slot is the top one.

 

That's a ruff explanation and high end system can have 2 or more "fastest" m.2/pcie connectors, you're going to add minimal latency because of the distance they need to travel but that's it.

 

Hoping it answers your question, have a good day!

Edited January 16 by Steace
Apparently can't read on morning