IBM PowerPC 604 User Manual page 431

Static branch prediction.
Mechanism by which software (for example,
compilers) can give a hint to the machine hardware about the
direction the branch is likely to take.
Sticky bit. A
bit that when set must be cleared explicitly.
Superscalar machine. A
machine that can issue multiple instructions
concurrently from a conventional linear instruction stream.
Supervisor mode.
The privileged operation state of the a processor. In
supervisor mode, software can access all control registers and can
access the supervisor memory space, among other privileged
operations.
U
Underflow. An error condition that occurs during arithmetic operations when
the result cannot be represented accurately in the destination register.
For example, underflow can happen if two floating-point fractions
are multiplied and the result is a single-precision number. The result
may require a larger exponent and/or mantissa than the single-
precision format makes available. In other words, the result is too
small to be represented accurately.
Unified cache.
Combined data and instruction cache.
User mode.
The unprivileged operating state of a processor. In user mode,
software can only access certain control registers and can only
access user memory space. No privileged operations can be
performed.
W
Write-through. A
memory update policy
in
which all processor write cycles
are written to both the cache and memory.
Glossary of Terms and Abbreviations Glossary-5
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