PCI speed

Dirk-Willem van Gulik dirkx at webweaving.org
Fri Mar 3 22:36:10 UTC 2017


Forgive me my ignorance - but for some cards - pciconf(8) nicely lists the speed of the bus:

> ciss0 at pci0:12:0:0:      class=0x010400 card=0x3243103c chip=0x323a103c rev=0x01 hdr=0x00
...
>     cap 10[70] = PCI-Express 2 endpoint max data 128(256) RO NS
>                  link x4(x8) speed 5.0(5.0)
>     cap 11[ac] = MSI-X supports 16 messages, enabled
>                  Table in map 0x10[0x1c2000], PBA in map 0x10[0x1c4000]
>   PCI-e errors = Correctable Error Detected
>                  Fatal Error Detected
>                  Unsupported Request Detected

and that matches exactly with what it is. While for other cards it does not seem to report that:

> mpt4 at pci0:7:8:1:        class=0x010000 card=0x10b01000 chip=0x00301000 rev=0x08 hdr=0x00
....
>     cap 01[50] = powerspec 2  supports D0 D1 D2 D3  current D0
>     cap 05[58] = MSI supports 1 message, 64 bit
>     cap 07[68] = PCI-X 64-bit supports 133MHz, 2048 burst read, 8 split transactions
>     cap 00[70] = unknown

and in fact seems to mis report the bus - this is a  PCIe Gen 2 x4 bus with a x8 Connector Width
holding  a LSI 22320SE Ultra320 SCSI dual channel PCIe X4 card.

How should one interpret this ?

Dw.



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