Content deleted Content added
remove redundancy |
oops |
||
Line 25:
The System/360 supports variable-length target instructions. It also supports modifying the target instruction in various ways before executing it. The target instruction [[data alignment|must start on an even-numbered byte]].<ref name="s360"/>
Some architectures support execution of a sequence of two instructions, notably the GE-600 series. The target instructions [[data alignment|must start on an even-numbered word]].<ref name="GE635"/>
Some architectures support an ''execute'' instruction which operates in a different [[Protection ring|protection and address relocation mode]]. For example, the [[Incompatible Timesharing System|ITS]] PDP-10 paging device supports a [[Protection ring|privileged-mode]] {{mono|XCTR}} 'execute relocated' instruction which allows memory reads, writes, or both to use the user-mode page mappings.<ref>{{cite web|first=J.|last=Holloway|title=Hardware Memo 2 - PDP-10 Paging Device|publisher=[[MIT AI Lab]]|date=February 20, 1970|page=11|url=http://www.bitsavers.org/pdf/mit/ai/ai_600dpi/HW_Memo_2_PDP-10_Paging_Device_Feb1970.pdf}}</ref> Similarly, the [[PDP-10#KL10|KL10]] variant of the PDP-10 supports the privileged instruction {{mono|PXCT}} 'previous context XCT'.<ref name="pdp10">{{cite manual|publisher=[[Digital Equipment Corporation]]|title=DECsystem-10, DECSYSTEM-20 Processor Reference Manual|id=AA-H391A-TK, AD-H391A-T1|date=June 1982|page=2{{hyphen}}63|url=https://www.livingcomputers.org/UI/UserDocs/Tops-10-v7-04/3_DECsystem-10_DECSYSTEM-20_Processor_Reference.pdf}}</ref>
| |||