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Alpha 21264/EV67 Hardware Reference Manual
Glossary–3
boot
Short for bootstrap. Loading an operating system into memory is called booting.
BSR
Boundary-scan register.
buffer
An internal memory area used for temporary storage of data records during input or
output operations.
bugcheck
A software condition, usually the response to software’s detection of an “internal incon-
sistency,” which results in the execution of the system bugcheck code.
bus
A group of signals that consists of many transmission lines or wires. It interconnects
computer system components to provide communications paths for addresses, data, and
control information.
byte
Eight contiguous bits starting on an addressable byte boundary. The bits are numbered
right to left, 0 through 7.
byte granularity
Memory systems are said to have byte granularity if adjacent bytes can be written con-
currently and independently by different processes or processors.
cache
See cache memory.
cache block
The smallest unit of storage that can be allocated or manipulated in a cache. Also
known as a cache line.
cache coherence
Maintaining cache coherence requires that when a processor accesses data cached in
another processor, it must not receive incorrect data and when cached data is modified,
all other processors that access that data receive modified data. Schemes for maintain-
ing consistency can be implemented in hardware or software. Also called cache consis-
tency.
cache fill
An operation that loads an entire cache block by using multiple read cycles from main
memory.
cache flush
An operation that marks all cache blocks as invalid.