I am curious to know if anybody working with Ice Lake has seen this behavior where the MemRD TLPs, from a "cpu(s)" issuing I/O Reads to an I/O device, are carrying varying RequesterID (RID) values that don't represent any enumerated devices (per lspci) in the system? The particular system in use is a Supermicro box with 2 CPU sockets, each socket comprised of a 16 core (2 thread/core) processor. I have not seen any correlation between issuing the I/O Read operation from a particular core and the RID that shows up in the respective MemRD TLP. Normally, I would have expected the RID to have been either 0x0000 or the BDF of the respective Root Port into which the device being read was plugged into. I assume this behavior is intended to increase I/O bandwidth and reduce latency by allowing even more outstanding I/O Reads than is normally afforded by the (per-device) Tag field of a MemRD TLP. I have been searching around, but having trouble finding specifics about this behavior in any specs or micro-architecture documents. If anybody knows of any pointers it would be greatly appreciated. Thanks in advance! Eric -- Eric Pilmore epilmore@xxxxxxxxxx http://gigaio.com Phone: (858) 775 2514 This e-mail message is intended only for the individual(s) to whom it is addressed and may contain information that is privileged, confidential, proprietary, or otherwise exempt from disclosure under applicable law. If you believe you have received this message in error, please advise the sender by return e-mail and delete it from your mailbox. Thank you.
