HP ML350 G9 with 4 GPUs: Pci-e transfers slow

[fp64]

Hi,
The hardware manual for the HP ML350 G9 says that of the four x16 pcie slots, 3 are full 16-electrical an one 8. When 3 gpus (a mix of MI50 and MI60), are mounted on the 16-e slots, the pcie transfer rates are as advertised. When a fourth card is added to the 8-e slot (now 4 in total ) all of them appear to slow down. Going thru the output of lspci -vvv, all four cards show

LnkCap: Port #0, Speed 16GT/s, Width x16, ...
...
LnkSta: Speed 16GT/s (ok), Width x16 (ok)
...

but actual transfer rates thru all slots are down as measured from inside an application. Any ideas what is going on? Is it possible to enforce the spec-sheet speeds?
==

 

[fp64]

Embarrassingly obvious once u know it. Went thru the bios flipping switches that were likely to affect the pci speed. Finally, the power setting did the trick - from 'Custom' to 'Performance'.