Engineering:PALcode
PALcode (Privileged Architecture Library code)[1][2] 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 firmware, providing a hardware abstraction layer for system software, covering features such as cache management, translation lookaside buffer (TLB) miss handling, interrupt handling, and exception handling. It evolved from a feature of the DEC PRISM architecture named Epicode.[3]
PALcode is Alpha machine code, running in a special mode[4] 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. PALcode is operating system-specific,[5] so different versions of PALcode are required by OpenVMS, Tru64 UNIX, and Windows NT. Tru64 UNIX PALcode is also used by NetBSD, FreeBSD, OpenBSD and Linux.
References
- ↑ Alpha Architecture Reference Manual. 2014. ISBN 978-1483294339. https://books.google.com/books?id=aYioBQAAQBAJ&q=very+flexible. "PALcode—Alpha's Very Flexible Privileged Software Library A Privileged Architecture Library (PALcode) is a set of subroutines that ..."
- ↑ "PALcode for Alpha Microprocessors System Design Guide". May 2, 1996. https://download.majix.org/dec/palcode_dsgn_gde.pdf. "PALcode for Alpha Microprocessors. System Design Guide. May 1996. This guide explains how to use the Privileged Architecture Library code."
- ↑ Neil Rieck. "Dave Cutler, PRISM, Mica, Emerald, etc.". http://neilrieck.net/docs/dave_cutler-prism-mica-emerald-etc.html.
- ↑ "PALcode - ES40 Emulator". http://www.es40.org/PALcode. "PALcode is Alpha machine code, running in a special mode that allows access to internal registers specific to the particular Alpha processor"
- ↑ "The Alpha AXP Processor". http://www.science.unitn.it/~fiorella/guidelinux/tlk/node140.html. "The Alpha AXP architecture uses a set of subroutines, call privileged architecture library code (PALcode). PALcode is specific to the operating system, the CPU ..."
External links
- Hewlett Packard OpenVMS FAQ (archived on May 11, 2011)
- "PALcode for Alpha Microprocessors System Design Guide". Digital Equipment Corporation. May 1996. http://download.majix.org/dec/palcode_dsgn_gde.pdf. Retrieved November 7, 2013.
- "Some simple PAL code". http://www.docstoc.com/docs/103863445/PAL.
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