64-bit Intel Xeon Processor MP with up to 8MB L3 Cache Specification Update

64-bit Intel
®
Xeon
®
Processor MP with up to 8 MB L3 Cache Specification Update 19
Errata
special cycle to be issued to the bus before the processor vectors to the machine check handler.
Once the chipset receives its last Stop Grant special cycle it is allowed to ignore any bus
activity from the processors. As a result, processor accesses to the machine check handler may
not be acknowledged, resulting in a processor hang.
Implication: The processor is unable to correctly report and/or recover from certain errors
Workaround: None identified.
Status: For the steppings affected, see the Summary Table of Changes.
U6 Debug mechanisms may not function as expected
Certain debug mechanisms may not function as expected on the processor. The cases are as
follows:
• When the following conditions occur: 1) An FLD instruction signals a stack overflow or
underflow, 2) the FLD instruction splits a page-boundary or a 64 byte cache line boundary, 3)
the instruction matches a Debug Register on the high page or cache line respectively, and 4)
the FLD has a stack fault and a memory fault on a split access, the processor will only signal
the stack fault and the debug exception will not be taken.
• When a data breakpoint is set on the ninth and/or tenth byte(s) of a floating-point (FP) store
using the Extended Real data type, and an unmasked FP exception occurs on the store, the
break point will not be captured.
• When any instruction has multiple debug register matches, and any one of those debug
registers is enabled in DR7, all of the matches should be reported in DR6 when the processor
goes to the debug handler. This is not true during a REP instruction. As an example, during
execution of a REP MOVSW instruction the first iteration a load matches DR0 and DR2 and
sets DR6 as FFFF0FF5h. On a subsequent iteration of the instruction, a load matches only
DR0. The DR6 register is expected to still contain FFFF0FF5h, but the processor will update
DR6 to FFFF0FF1h.
• A Data breakpoint that is set on a load to uncacheable memory may be ignored due to an
internal segment register access conflict. In this case the system will continue to execute
instructions, bypassing the intended breakpoint. Avoiding having instructions that access
segment descriptor registers e.g. LGDT, LIDT close to the UC load, and avoiding serialized
instructions before the UC load will reduce the occurrence of this erratum.
Implication: Certain debug mechanisms do not function as expected on the processor.
Workaround: None identified.
Status: For the steppings affected, see the Summary Table of Changes.
U7 Cascading of performance counters does not work correctly when forced
overflow is enabled
Problem: The performance counters are organized into pairs. When the CASCADE bit of the Counter
Configuration Control Register (CCCR) is set, a counter that overflows will continue to count in
the other counter of the pair. The FORCE_OVF bit forces the counters to overflow on every non-
zero increment. When the FORCE_OVF bit is set, the counter overflow bit will be set but the
counter no longer cascades.
Implication: The performance counters do not cascade when the FORCE_OVF bit is set.
Workaround: None identified.
Status: For the steppings affected, see the Summary Table of Changes.