Datasheet

Reset
Intel
®
Xeon
®
Processor C5500/C3500 Series
Datasheet, Volume 1 February 2010
370 Order Number: 323103-001
10.0 Reset
10.1 Introduction
This chapter describes specific aspects of various hardware resets.
10.1.1 Types of Reset
These are the types of reset:
• Power Good Reset
Power good reset is invoked by the de-assertion of the VCCPWRGOOD signal and is
part of power-up reset. This reset clears sticky bits, clears all system states, and
downloads fuses. Power-good reset destroys program state, can corrupt memory
contents, and destroys error logs.
•Warm Reset
Warm reset is invoked by the assertion of the PLTRST# signal and is part of both
the power-up and power good reset sequences. Warm reset is the “normal”
component reset, with relatively short latency and fewer side-effects than power
good reset. It preserves sticky bits (e.g. error logs and power-on configuration).
Warm reset destroys the program state and can corrupt memory contents, so it
should only be used as a means to un-hang a system while preserving error logs
that might provide a trail to the fault that caused the hang. Warm reset can be
initiated by code running on a processor, SMBus, or PCI agents. Warm reset is not
guaranteed to correct all illegal configurations or malfunctions. Software can
configure sticky bits in the IIO to disable interfaces that will not be accessible after
a warm reset. Signaling errors or protocol violations prior to reset (from Intel
®
QPI,
DMI, or PCI-Express) may hang interfaces that are not cleared by a warm reset.
• PCI Express* Reset
A PCI Express reset combines a physical-layer reset and a link-layer reset for a PCI-
Express port. There are individual PCI Express resets for each PCI Express port.
•SMBus Reset
An SMBus reset resets only the slave SMBus controller. The slave SMBus controller
consists of the protocol engine and SMBus-specific “data state,” such as the
command stack. An SMBus reset does not reset any state that is observable
through any other interface into the component.
• CPU Only Reset (also known as CPU warm reset)
Software can reset the processing cores and uncore independant of the IIO by
setting the IIO.SYRE.CPURESET bit. The BIOS uses this for changing Intel
®
QPI
frequency.
10.1.2 Trigger, Type, and Domain Association
Table 126 indicates which core reset domains are affected by each reset type, and
which reset triggers initiated each reset type.