Question Explanation GPU and CPU lanes and PCIe x1 - x16

Sep 23, 2021
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Hi Guys,

I'm puzzled and I can't seem to find the good answer online!!! Searched everywhere...

I have a MB Asrock H510 pro btc: 6x PCIe 3.0 x16 slots but 1@x16 and 5@x1... and a miner port M_Port1 at x1.
We put a CPU Intel G6400 which has max 16 PCIe lanes and GPU execution units 12.
The GPU's we are using are 6x AMD Radeon RX 6600 XT and doesn't need a lot of throughput(?) since operates at ~60W for 32MH/s ETH which is exactly as it should be..

Now we might be planning to add more GPU's to the same motherboard... correct me if I'm wrong please:
  • each PCIe port can be set on Gen 1-4 which changes transfer throughput depending on what kind of PCIe number it uses (x1 till x16).
  • true that the one PCIe 3.0 x16 uses "16 lanes" from the CPU?
  • how can I see how many CPU lanes are used per PCIe?
  • how many GPU's (RX6600XT) can i connect to the x16 slot and how many GPU's can i connect to the x1 slot (with the help of risers ofcourse)....
  • does setting the Gen 1.0 - 4.0 matter for the amount of GPU's i can connect to the motherboard?
Thanks in advance
 

popatim

Titan
Moderator
You'll need to read your manual to see how the various pcie slots are getting their lanes.

You have 16 lanes available from the CPU plus 4 more that are dedicated to communication the the Northbridge chip. These are commonly split between 2 slots for an x8/x8 config but your board may break it down further.

The H510 chipset has 6 lanes to distribute, thats it just 6 lanes. These could potentially be split down to 6 x1 slots.

They do make PLX chips that work like network switches and can share pcie lanes across several slots to accommodate more slots. You'll need to investigate your manual to see if your board is using those. You'll typically see these in boards that claim to have 4 x16 slots all running at x16.. They actually work pretty well as long none of the slots require full bandwidth.
 
Sep 23, 2021
2
0
10
0
You'll need to read your manual to see how the various pcie slots are getting their lanes.

You have 16 lanes available from the CPU plus 4 more that are dedicated to communication the the Northbridge chip. These are commonly split between 2 slots for an x8/x8 config but your board may break it down further.

The H510 chipset has 6 lanes to distribute, thats it just 6 lanes. These could potentially be split down to 6 x1 slots.

They do make PLX chips that work like network switches and can share pcie lanes across several slots to accommodate more slots. You'll need to investigate your manual to see if your board is using those. You'll typically see these in boards that claim to have 4 x16 slots all running at x16.. They actually work pretty well as long none of the slots require full bandwidth.
Alright thanks already! in the manual and online I cannot find anything about the PLX chip.... so i doubt it uses that

You say the H510 has 6 lanes to distribute... does that mean i cannot use 1 to 4 riser adapter + 4 risers to connect up to 4 GPUs per PCIe?

Also i have the "miner" port which should be able to support another GPU (through 1 to 4 riser kit... potentially 4 GPU's)?

and i heard i can connect the 1 to 4 riser kit even to the PCIe x1 slots!?
 
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popatim

Titan
Moderator
From your Motherboard Manual, on page 2, its pretty obvious how the slots are broken down and what is providing the pcie lanes.

• 6 x PCI Express 3.0 x16 Slots (PCIE1 at x16 / PCIE2~6 at x1)

As for your mining port: Also from your manual
• 1 x Mining Port (M_Port1 at x1)*
* Support USB Type Riser kit


I'd suggest finding our what a USB type riser is....


As for your 1 to 4 riser I cannot answer that . I don't know which you have and what its requirements are but ... that would all be found in it's manual.
 
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