secondary cache
<memory management> (Or "second level cache", "level two cache", "L2
cache") A larger, slower cache between the primary cache and main memory.
Whereas the primary cache is often on the same integrated circuit as the central
processing unit (CPU), a secondary cache is usually external.
(1997-06-25)
Nearby terms:
SEC « SECC « SECD machine « secondary cache »
secondary damage » secondary key » secondary storage
secondary damage
When a fatal error occurs (especially a segfault) the immediate cause may be
that a pointer has been trashed due to a previous fandango on core. However,
this fandango may have been due to an *earlier* fandango, so no amount of
analysis will reveal (directly) how the damage occurred. "The data structure was
clobbered, but it was secondary damage."
By extension, the corruption resulting from N cascaded fandangoes on core is
"Nth-level damage". There is at least one case on record in which 17 hours of
grovelling with "adb" actually dug up the underlying bug behind an instance of
seventh-level damage! The hacker who accomplished this near-superhuman feat was
presented with an award by his fellows.
[Jargon File]
Nearby terms:
SECC « SECD machine « secondary cache « secondary
damage
» secondary key » secondary storage » second
generation computer
secondary key
<database> A candidate key which is not selected as a primary key.
(1997-04-26)
Nearby terms:
SECD machine « secondary cache « secondary damage «
secondary key » secondary storage » second
generation computer » second generation language
secondary storage
<storage> Any non-volatile storage medium that is not directly accessible
to the processor. Memory directly accessible to the processor includes main
memory, cache and the CPU registers. Secondary storage includes hard drives,
magnetic tape, CD-ROM, DVD drives, floppy disks, punch cards and paper tape.
Secondary storage devices are usually accessed via some kind of controller. This
contains registers that can be directly accessed by the CPU like main memory
("memory mapped"). Reading and writing these registers can cause the device to
perform actions like reading a block of data off a disk or rewinding a tape. See
also DMA.
Programs and data stored in secondary storage must first be loaded into main
memory before the processor can use them.
(1997-11-05)
Nearby terms:
secondary cache « secondary damage « secondary key «
secondary storage » second generation computer »
second generation language » second level cache
second generation computer
<architecture> A computer built from transistors, designed between the
mid-1950s and mid-1960s.
Ferrite core memory and magnetic drums replaced cathode ray tubes and delay-line
storage for main memory. Index registers and floating point arithmetic hardware
became widespread. Machine-independent high level programming languages such as
ALGOL, COBOL and Fortran were introduced to simplify programming.
I/O processors were introduced to supervise input-output operations
independently of the CPU thus freeing the CPU from time-consuming housekeeping
functions. The CPU would send the I/O processor an initial instruction to start
operating and the I/O processor would then continue independently of the CPU.
When completed, or in the event of an error, the I/O processor sent an interrupt
to the CPU.
Batch processing became feasible with the improvement in I/O and storage
technology in that a batch of jobs could be prepared in advance, stored on
magnetic tape and processed on the computer in one continuous operation placing
the results on another magnetic tape. It became commonplace for auxiliary, small
computers to be used to process the input and output tapes off-line thus leaving
the main computer free to process user programs. Computer manufacturers began to
provide system software such as compilers, subroutine libraries and batch
monitors.
With the advent of second generation computers it became necessary to talk about
computer systems, since the number of memory units, processors, I/O devices, and
other system components could vary between different installations, even though
the same basic computer was used.
The instruction repertoire of the IBM 7094 (a typical second generation machine)
had over 200 instructions including data transfer instructions for transferring
a word of information between the CPU and memory or between two CPU registers;
fixed-point and floating point arithmetic instructions; logic instructions (AND,
OR etc.); instructions for modifying index registers; conditional and
unconditional branching; subroutines; input-output operations for transferring
data between I/O devices and main memory.
(1996-11-25)
Nearby terms:
secondary damage « secondary key « secondary storage
«
second generation computer » second generation
language » second level cache » second normal form
second generation language
assembly language
See also first generation language, third generation language.
Nearby terms:
secondary key « secondary storage « second
generation computer « second generation language
» second level cache » second normal form »
Second-Order Lambda-calculus
second level cache
secondary cache
Nearby terms:
secondary storage « second generation computer «
second generation language « second level cache
» second normal form » Second-Order Lambda-calculus
» second-system effect
second normal form
database normalisation
Nearby terms:
second generation computer « second generation
language « second level cache « second normal
form » Second-Order Lambda-calculus »
second-system effect » sector interleave
Second-Order Lambda-calculus
<language> (SOL) A typed lambda-calculus.
["Abstract Types have Existential Type", J. Mitchell et al, 12th POPL, ACM 1985,
pp. 37-51].
(1995-07-29)
Nearby terms:
second generation language « second level cache «
second normal form « Second-Order Lambda-calculus
» second-system effect » sector interleave » sector
interleaving
second-system effect
(Sometimes, more euphoniously, "second-system syndrome") When one is designing
the successor to a relatively small, elegant, and successful system, there is a
tendency to become grandiose in one's success and design an elephantine
feature-laden monstrosity. The term was first used by Fred Brooks in his classic
"The Mythical Man-Month. It described the jump from a set of nice, simple
operating systems on the IBM 70xx series to OS/360 on the 360 series. A similar
effect can also happen in an evolving system; see Brooks's Law, creeping
elegance, creeping featurism. See also Multics, OS/2, X, software bloat.
[Jargon File]
Nearby terms:
second level cache « second normal form «
Second-Order Lambda-calculus « second-system
effect » sector interleave » sector interleaving
» sector map
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