IBM PowerPC 604 User Manual page 428

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Cache coherency. Caches are coherent if a processor performing a read from
its cache is supplied with data corresponding to the most recent value
written to memory or to another processor's cache.
Cast-outs. Cache blocks that must be written to memory when a snoop miss
causes the least recently used section with modified data to be
replaced.
Context synchronization. Context synchronization as the result of specific
instructions (such as isync or rfi) or when certain events occur (such
as an exception). During context synchronization, all instructions in
execution complete past the point where they can produce an
exception; all instructions in execution complete in the context in
which they began execution; all subsequent instructions are fetched
and executed in the new context.
D
Denormalized number. A nonzero floating-point number whose exponent
has a reserved value, usually the format's minimum, and whose
explicit or implicit leading significand bit is zero.
E
Exception. A condition encountered by the processor that requires special
Glossary-2
processing.
Exception handler. A software routine that executes when an exception
occurs. Nonnally, the exception handler corrects the condition that
caused the exception, or performs some other meaningful task (such
as aborting the program that caused the exception). The addresses of
the exception handlers are defined by a two-word exception vector
that is branched to automatically when an exception occurs.
Execution synchronization. All instructions in execution are architecturally
complete before beginning execution (appearing to begin execution)
of the next instruction. Similar to context synchronization but doesn't
force the contents of the instruction buffers
to
be deleted and
re fetched.
Exponent. The component of a binary floating-point number that nonnally
signifies the integer power to which two is raised in detennining the
value of the represented number. Occasionally the exponent is called
the signed or unbiased exponent.
PowerPC 604 RISC Microprocessor User's Manual