intersil 6100

Computing Dictionary

Intersil 6100 definition

programming
(IMS 6100) A single chip design of the DEC PDP-8 minicomputer. The old PDP-8 design was very strange, and if it hadn't been popular, an awkward CPU like the 6100 would never been designed.
The 6100 was a 12-bit processor, which had three registers: the PC, AC (accumulator), and MQ. All 2-operand instructions read AC and MQ and wrote back to AC. It had a 12-bit address bus, limiting RAM to only 4K. Memory references were 7-bit, offset either from address 0, or from the PC page base address (PC AND 7600 oct).
It had no stack. Subroutines stored the PC in the first word of the subroutine code itself, so recursion required fancy programming.
4K RAM was pretty much hopeless for general purpose use. The 6102 support chip (included in the 6120) added 3 address lines, expanding memory to 32K the same way that the PDP-8/E expanded the PDP-8. Two registers, IFR and DFR, held the page for instructions and data respectively (IFR was always used until a data address was detected). At the top of the 4K page, the PC wrapped back to 0, so the last instruction on a page had to load a new value into the IFR if execution was to continue.
(2003-04-04)
The Free On-line Dictionary of Computing, © Denis Howe 2010 http://foldoc.org
Cite This Source
Explore Dictionary.com
Previous Definition: intersidereal
Next Definition: intersil 6120
Words Near: intersil 6100
More from Thesaurus.com
Synonyms and Antonyms for intersil 6100
More from Reference.com
Search for articles containing intersil 6100
More from Dictionary.com Translator
Dictionary.com Word FAQs

Dictionary.com presents 366 FAQs, incorporating some of the frequently asked questions from the past with newer queries.

Copyright © 2014 Dictionary.com, LLC. All rights reserved.
  • Please Login or Sign Up to use the Recent Searches feature