process - homework questions from stallings book -

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alt text

a.why there many wait states in in vms/vax process states ?

all of waits except 1 have memory swapping or thread swapping.

the vax architecture had virtual addressing. program access 1 gigabyte of address space, huge in 1977. if remember correctly, 32 or 64 megabytes of memory standard. meant programs access more memory machine had. vax managed virtual memory paging memory , disk drive.

multiple users use vax. accomplished multiple user threads. since processor execute 1 instruction @ time, 1 thread active @ time. generally, thread run until i/o instruction encountered. thread swapped out, , other threads allowed execute, while i/o instruction completed.

if want feel in olden days, read tracy kidder's "soul of new machine". it's story of team developed data general eclipse mv/8000.


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