PCIe x16 shared slots

[Tristerin]

 

Motherboard in question: ASUS B350 Prime Plus 

Pics below

Manual link:

https://dlcdnets.asus.com/pub/ASUS/mb/SocketAM4/PRIME_B350-PLUS/E13723_PRIME_B350-PLUS_UM_V3_WEB_20171114.pdf

 

Can anyone help me understand what this means?  From what I understand it is:

 

PCIe x16 slot 1 is handled by the CPU

 

PCIe x16 slot 2 is handled by the Chipset, but is shared - so at max slot 2 can only run at x4 with a GPU populated (Crossfire)?  I do not have M.2 installed on this mobo

 

Thank you!

 

[Electronics Wizardy]

That shared chart seems to be irp, not bandwidth.

 

Yea, its limited to x4 from the chipset, you don't want to use this board for multigpu usages.

[NumLock21]

Yes that is correct, 1st PCIe x16 slot will run at x16 which takes lanes directly from your CPU. The 2nd PCIe x16 slot uses lanes from the chipset and the maximum it can have is x4. The 2nd PCIe x16 shares bandwidth with the PCIe x1 slots, so if you plug a card into one of those, then you're 2nd x16 slot will operate at a lower bandwidth.

Also it depends on the CPU, using an Athlon, then the 1st x16 slot is limited to x8.

 

[Tristerin]

10-4 I remembered I shouldn't on this board, cause someone told me (but not the why) and now I understand (would saturate the lanes on the second GPU when in use.  Have a Fury X on the way, looks like if I want to Xfire these (2x Fury non X) I can only do it on my B450 or my FX system

[NumLock21]

2 minutes ago, Tristerin said:

10-4 I remembered I shouldn't on this board, cause someone told me (but not the why) and now I understand (would saturate the lanes on the second GPU when in use.  Have a Fury X on the way, looks like if I want to Xfire these (2x Fury non X) I can only do it on my B450 or my FX system

Running dual GPUs, then always get a board that can do x8/x8 not this x16/x4 nonsense.

[Electronics Wizardy]

6 minutes ago, Tristerin said:

10-4 I remembered I shouldn't on this board, cause someone told me (but not the why) and now I understand (would saturate the lanes on the second GPU when in use.  Have a Fury X on the way, looks like if I want to Xfire these (2x Fury non X) I can only do it on my B450 or my FX system

b450 has the same limit of only one x16 slot from the cpu.

[Tristerin]

3 minutes ago, Electronics Wizardy said:

b450 has the same limit of only one x16 slot from the cpu.

Yea was just checking on that ASRock board, my old ASUS FX board can, guess that's where these are going!

[Electronics Wizardy]

Just now, Tristerin said:

Yea was just checking on that ASRock board, my old ASUS FX board can, guess that's where these are going!

Id still use one gpu, crossfire has a lot of issues, and fx will probalby be more of a limit than crossfile with a x4 gpu.

 

 

[Tristerin]

Just now, Electronics Wizardy said:

Id still use one gpu, crossfire has a lot of issues, and fx will probalby be more of a limit than crossfile with a x4 gpu.

 

 

Just for the fun