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Supermicro Epyc 7401 PCI Bus Resource Problem

Question asked by kchow on Jul 3, 2019
Latest reply on Aug 15, 2019 by ray_m

We have a Supermicro dual socket Epyc 7401 2u server and see that BIOS assigns PCI Root Bus numbers of 0x00 0x10 0x20 0x30 0x40 0x50 0x60 and 0x70 for the 8 numa nodes.  Each of the nodes would therefore have a total of 16 PCI buses available.

 

When IO devices are connected  to the server (via a host adapter card connecting to a PCIe Switch), we see that BIOS can assimilate the PCI buses from adjacent nodes and assign it to the PCI Root Bus in need.  For example, when a Celestica JBOF (requires 26+ PCI Buses) is connected to Root Bus 0x20,  PCI buses from Root PCI Bus 0x30 and 0x40 are reassigned such that Root Bus 0x20 ends up with 48 PCI Buses.

 

A few questions....

1) only 128 of the 256 PCI Buses are being configured by BIOS.  Is it possible to have PCI Buses 0x80-0xFF configured/assigned?

2) when additional IO is added to Root Bus 0x20 (e.g. a 2nd Celestica JBOF), the number of PCI Buses assigned does not go beyond 48.  Is there a way to go beyond 48 PCI Buses?  Using the last half (0x80-0xff) of the PCI Buses might be a start.

 

Regards

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