DEC 4000 AXP Service Manual page 222

latency
The amount of time it takes the system to respond to an event.
LDC
See local disk converter.
LED
Light-emitting diode. A semiconductor device that glows when supplied with
voltage.
local disk converter (LDC)
Refers to modules that regulate voltages for fixed-media storage devices. An
LDC module is located in each of the fixed-media storage compartments (A–D),
provided that the compartment is not storageless.
longword
Four contiguous bytes starting on an arbitrary byte boundary. The bits are
numbered from right to left, 0 through 31.
loopback tests
Diagnostic tests used to isolate a failure by testing segments of a particular
control or data path.
low-level language
Any language that exposes the details of the hardware implementation to the
programmer. Typically this refers to assembly languages that allow direct
hardware manipulation. See also high-level language.
machine check/interrupts
An operating system action triggered by certain system hardware-detected errors
that can be fatal to system operation. Once triggered, machine check handler
software analyzes the error.
mailbox
A memory data structure used to communicate between different components of
the system.
masked write
A write cycle that only updates a subset of a nominal data block.
Glossary–12