Date: Tue, 14 Mar 2017 09:41:53 -0400 From: Andrew Gallatin <gallatin@cs.duke.edu> To: Dirk-Willem van Gulik <dirkx@webweaving.org>, freebsd-hackers@freebsd.org Subject: Re: PCI speed Message-ID: <061c8bd6-63d1-2e59-2ab0-c4b48c201e96@cs.duke.edu> In-Reply-To: <03745A05-DE0E-4071-B432-BFE58C3A7E16@webweaving.org> References: <03745A05-DE0E-4071-B432-BFE58C3A7E16@webweaving.org>
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On 03/03/2017 17:34, Dirk-Willem van Gulik wrote: > Forgive me my ignorance - but for some cards - pciconf(8) nicely lists the speed of the bus: > >> ciss0@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@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. > > The mpt seems to be a PCI-X device, not a PCI Express device. So it is likely that the add-on card actually contains a PCI-e to PCI-X bridge chip. PCI Express was *very* hard to get right in the early days of Gen 1 before companies had built up large PCIe IP libraries and test suites. So a lot of companies with existing PCI and PCI-X products shipped "native" PCIe products that were actually composed of a PCIe connector with a third part PCIe to PCI-X bridge. It might be interesting to see what's upstream from the bus. I'd expect there is a PLX (or maybe IDT) device in there. Drew
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