PALcode (Privileged Architecture Library code) is the name used by DEC in the
Alpha instruction set architecture (ISA) for a set of functions in the
System Reference Manual (SRM) or
AlphaBIOS
Advanced RISC Computing (ARC) is a specification promulgated by a defunct consortium of computer manufacturers (the Advanced Computing Environment project), setting forth a standard MIPS RISC-based computer hardware and firmware environment ...
firmware, providing a
hardware abstraction layer
Hardware abstractions are sets of routines in software that provide programs with access to hardware resources through programming interfaces. The programming interface allows all devices in a particular class ''C'' of hardware devices to be acce ...
for system software, covering features such as cache management,
translation lookaside buffer
A translation lookaside buffer (TLB) is a memory cache that stores the recent translations of virtual memory to physical memory. It is used to reduce the time taken to access a user memory location. It can be called an address-translation cache. ...
(TLB) miss handling, interrupt handling, and exception handling. It evolved from a feature of the
DEC PRISM
PRISM (Parallel Reduced Instruction Set Machine) was a 32-bit RISC instruction set architecture (ISA) developed by Digital Equipment Corporation (DEC). It was the outcome of a number of DEC research projects from the 1982–1985 time-frame, and t ...
architecture named Epicode.
PALcode is Alpha machine code, running in a special mode that also allows access to internal registers specific to the particular Alpha processor implementation. Thus, it is somewhere between the role of
microcode and of a hardware
emulator
In computing, an emulator is hardware or software that enables one computer system (called the ''host'') to behave like another computer system (called the ''guest''). An emulator typically enables the host system to run software or use pe ...
. PALcode is
operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs.
Time-sharing operating systems schedule tasks for efficient use of the system and may also i ...
-specific,
so different versions of PALcode are required by
OpenVMS,
Tru64 UNIX, and
Windows NT
Windows NT is a proprietary graphical operating system produced by Microsoft, the first version of which was released on July 27, 1993. It is a processor-independent, multiprocessing and multi-user operating system.
The first version of Win ...
. Tru64 UNIX PALcode is also used by
NetBSD,
FreeBSD,
OpenBSD and
Linux
Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, w ...
.
References
External links
Hewlett Packard OpenVMS FAQ(archived on May 11, 2011)
*
*
DEC hardware
Firmware
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