# dmesg
...
0000:03:00.0: 32.000 Gb/s available PCIe bandwidth, limited by 2.5 GT/s x16 link at 0000:00:0b.0 (capable of 64.000 Gb/s with 5 GT/s x16 link)
...

Как с этим бороться?

# lspci -v -s 0000:00:0b.0
00:0b.0 PCI bridge: Advanced Micro Devices, Inc. [AMD/ATI] RD890/RD990 PCI to PCI bridge (PCe])
        Flags: bus master, fast devsel, latency 0, IRQ 29, NUMA node 0
        Bus: primary=00, secondary=03, subordinate=03, sec-latency=0
        I/O behind bridge: 0000e000-0000efff
        Memory behind bridge: fcf00000-febfffff
        Prefetchable memory behind bridge: 00000000ce000000-00000000dfffffff
        Capabilities: [50] Power Management version 3
        Capabilities: [58] Express Root Port (Slot+), MSI 00
        Capabilities: [a0] MSI: Enable+ Count=1/1 Maskable- 64bit-
        Capabilities: [b0] Subsystem: Advanced Micro Devices, Inc. [AMD/ATI] RD890/RD990 PCI
        Capabilities: [b8] HyperTransport: MSI Mapping Enable+ Fixed+
        Capabilities: [100] Vendor Specific Information: ID=0001 Rev=1 Len=010 <?>
        Capabilities: [190] Access Control Services
        Kernel driver in use: pcieport