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Guy Harris (talk | contribs) →Applications: Help out readers that have neither heard of "sub verbo" nor know that "s.v." stands for "sub verbo". |
it would be good to find a source for why XCT is out of fashion |
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Fewer 1970s designs include ''execute'' instructions. An ''execute'' instruction was proposed for the [[PDP-11]] in 1970,<ref name="pdp11x">{{cite web|first=Ad|last=van de Goor|title=The Execute Instruction|id=PDP-11/40 Technical Memorandum 18|date=September 21, 1970|url=http://bitsavers.informatik.uni-stuttgart.de/pdf/dec/pdp11/memos/700921_The_Execute_Instruction.pdf}}</ref> but never implemented for it;<ref name="pdp11">{{cite manual|publisher=[[Digital Equipment Corporation]]|title=PDP11 Processor Handbook: PDP11/04/34a/44/60/60|date=1979|url=http://bitsavers.org/pdf/dec/pdp11/handbooks/PDP11_Handbook1979.pdf}}</ref> its successor, the [[VAX]], also had no ''execute'' instruction.<ref>{{cite manual|publisher=[[Compaq Computer Corporation]]|title=VAX MACRO and Instruction Set Reference Manual|id=AA-PS6GD-TE|date=April 2001|url=https://www.ece.lsu.edu/ee4720/doc/vax.pdf}}</ref> Architectures with an ''execute'' instruction include: the [[ND812|Nuclear Data 812]] minicomputer (1971) (<code>XCT</code>),<ref>{{cite manual|publisher=[[Nuclear Data, Inc.]]|title=Principles of Programming the ND812 Computer|date=1971|page=4{{hyphen}}4|url=http://bitsavers.trailing-edge.com/pdf/nd/ND812/ND812_Prog.pdf}}</ref> the Texas Instruments [[TI-990]] (1975) (<code>X</code>),<ref>{{cite manual|publisher=[[Texas Instruments]]|title=990 Computer Family Systems Handbook|page=3{{hyphen}}28|url=http://www.bitsavers.org/pdf/ti/990/945250-9701_990_Computer_Family_Systems_Handbook_3ed_May76.pdf}}</ref> and the microprocessor implementation of the same instruction set architecture, the [[TMS9900]] microprocessor (1976) (<code>X</code>).<ref>{{cite manual|publisher=[[Texas Instruments]]|title=TMS 9900 Microprocessor Data Manual|date=December 1976|page=24|url=http://datasheets.chipdb.org/TI/9900/TMS9900_DataManual.pdf}}</ref>
Modern instruction sets do not include ''execute'' instructions because they interfere with [[instruction pipeline|pipelining]] and other optimizations.{{citation needed|date=July 2021}}
==Semantics==
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