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Guy Harris (talk | contribs) →B5000: Mention all three models in the section header, and link the list of models to Burroughs Large Systems#B5000, B5500, and B5700. Mention the word length and the flag bit, and give references. |
Guy Harris (talk | contribs) →B6500: Indicate that words have 48 data bits and 3 tag bits (4 tag bits in later machines?), and that there are several descriptor types, with tag bits used to indicate descriptors, with references. List the various Bxxxx machines in the series, and indicate that the A-series machines were both from Burroughs and Unisys |
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</ref> [[Burroughs large systems descriptors|Descriptors]] have the uppermost bit set in the word. They reside in either the Program Reference Table (PRT) or the stack, and contain a ''presence bit'' indicating whether the data are present in memory. There are distinct data and program descriptors.<ref name=oper />{{rp|pages = 4{{hyp}}2-4{{hyp}}4}}
====B6500, B7500 and successors====
Words in the B6500 and its successors have 48 bits of data and 3 tag bits.<!--4 bits in later machines?--><ref name="b6500-ref-man">{{cite book |url=http://www.bitsavers.org/pdf/burroughs/LargeSystems/B6500_6700/1043676_B6500_RefMan_Sep69.pdf |title=B6500 Information Processing Systems Reference Manual |publisher=Burroughs |date=September 1969}}</ref>{{rp|page=2{{hyp}}1}} The tag bits indicate the type of data contained in the word; there are several descriptor types, indicated by different tag bit values.<ref name="b6500-ref-man" />{{rp|pages=6{{hyp}}5-6{{hyp}}10}}
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===Multics architectures===
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