Specification Update 37
BV56. PCI Express* Gen3 Receiver Return Loss May Exceed Specifications
Problem: The PCIe Base Specification includes a graph that sets requirements for maximum
receiver return loss versus frequency. Due to this erratum, the receiver return loss for
common mode and differential mode may exceed those requirements at certain
frequencies. Under laboratory conditions, Intel has observed violations of as much as
1 dB.
Implication: The PCI Express Gen3 Base Specification for receiver return loss may be exceeded. No
functional failures have been observed due to this erratum.
Workaround: None identified.
Status: For the steppings affected, see the Summary Tables of Changes.
BV57. Direct Access Via VT-d to The Processor Graphics Device M ay Le ad to a System Hang
Problem: Under a complex set of conditions, while using VT-d (Virtualization Technology for
Directed I/O) with the processor graphics device, direct access to the virtualized
processor graphics device can lead to a system hang or restart.
Implication: Systems providing direct access to processor graphics device via VT-d may hang or
restart. Intel has not observed this erratum with any commercially available system.
Workaround: VMM’s should ensure that all processor graphics device interactions conform to
guidance published in the Intel® Open Source HD Graphics Programmer's Reference
Manual and driver writers guide.
Status: For the steppings affected, see the Summary Tables of Changes.
BV58. An Event May Intervene Before a System Management Interrupt That Results from IN or INS
Problem: If an I/O instruction (IN, INS, OUT, or OUTS) results in an SMI (system-management
interrupt), the processor will set the IO_SMI bit at offset 7FA4H in SMRAM. This
interrupt should be delivered immediately after execution of the I/O instruction so that
the software handling the SMI can cause the I/O instruction to be re-executed. Due to
this erratum, it is possible for another event (e.g., a nonmaskable interrupt) to be
delivered before the SMI that follows the execution of an IN or INS instruction.
Implication: If software handling an affected SMI uses I/O instruction restart, the handler for the
intervening event will not be executed.
Workaround: The SMM handler has to evaluate the saved context to determine if the SMI was
triggered by an instruction that read from an I/O port. The SMM handler must not
restart an I/O instruction if the platform has not been configured to generate a
synchronous SMI for the recorded I/O port address.
Status: For the steppings affected, see the Summary Tables of Changes.