System information

AlphaServer 800 Service Guide
5-2
5.1 Fault Detection and Reporting
Table 5-1 provides a summary of the fault detection and correction components of
AlphaServer 800 systems.
Generally, PALcode handles exceptions as follows:
• The PALcode determines the cause of the exception.
• If possible, it corrects the problem and passes control to the operating system for
reporting before returning the system to normal operation.
• If error/event logging is required, control is passed through the system control
block (SCB) to the appropriate exception handler.
Table 5-1 AlphaServer 800 Fault Detection and Correction
Component Fault Detection/Correction Capability
CPU Daughter Board
Alpha 21164 microprocessor Contains error detection and correction (EDC)
logic for data cycles. There are check bits
associated with all data entering and exiting the
microprocessor.
A single-bit error on any of the four longwords
being read can be corrected (per cycle). A
double-bit error on any of the four longwords
being read can be detected (per cycle).
Backup cache (B-cache) EDC check bits on the data store, and parity on
the tag address store and tag control store.
Memory Subsystem
Memory DIMMs EDC logic protects data by detecting and
correcting data cycle errors. A single-bit error on
any of the four longwords can be corrected (per
cycle). A double-bit error on any of the four
longwords being read can be detected (per cycle).
Motherboard
SCSI controller SCSI data parity is generated.
EISA-to-PCI bridge chip PCI data parity is generated.