Sun Microelectronics
362
UltraSPARC User’s Manual
unassigned:
A value (for example, an ASI number), the semantics of which are not archi-
tecturally mandated and which may be determined independently by each
implementation (preferably within any guidelines given).
undefined:
An aspect of the architecture that has deliberately been left unspecified. Soft-
ware should have no expectation of, nor make any assumptions about, an
undefined feature or behavior. Use of such a feature may deliver random
results, may or may not cause a trap, may vary among implementations, and
may vary with time on a given implementation.
unimplemented:
An architectural feature that is not directly executed in hardware because it is
optional or is emulated in software.
unpredictable:
Synonymous with
undefined
.
unrestricted:
An adjective used to describe an address space identifier (ASI) that may be
used regardless of the processor mode; that is, regardless of the value of
PSTATE.PRIV.
virtual address:
An address produced by a processor that maps all system-wide, program-vis-
ible memory. Virtual addresses usually are translated by a combination of
hardware and software to physical addresses, which can be used to access
physical memory.
writeback:
The process of writing a dirty cache line back to memory before it is refilled.
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