The DEC VAX-11 instruction set had SVPCTX and LDPCTX for the kernel which made context switch simple. But they were reserved instructions; so they couldn't be u

The DEC VAX-11 instruction set had SVPCTX and LDPCTX for the kernel which made context switch simple. But they were reserved instructions; so they couldn't be used for setjmp() and longjmp(). VAX-11 also had queue instructions which made rescheduling simple. This was basically: SETIPL SVPCTX INSQUE FFS REMQUE LDPCTX SETIPL Yeah, there was a little more. See page 188 of ... http://bitsavers.informatik.uni-stuttgart.de/pdf/dec/vax/vms/training/EY-0016E-SG-0001_VMS_Internals_Student_Workbook_1982.pdf http://bitsavers.informatik.uni-stuttgart.de/pdf/dec/vax/vms...