intel's Vanderpool and virtualization in general 1669

the context change is with respect to permissions, address space, registers, etc. not with respect to end resource control. this is analogous to some of the GNOSIS stuff ... which turned into keykos. at one point keykos people made some mention that they could do (some kinds of?) transactions more efficiently than TPF (transaction processing facility kernel that is used by airline res and financial transaction systems ... and grew out of the old airline control program).

going back to OS-360 they have a really heavy weight dispatching unit with task control block (TCB). lots of online and transactions systems would create a large subsystem under OS-360 and then implement their own internal dispatching & scheduling (to avoid the really heavy weight operation of the main dispatcher); things like cics, ims, atm transaction stuff, etc.

somewhere along the way, SRBs were created for MVS (basically a light weight kernel threaded mechanism ... my vague recollection was that STL & IMS group were heavily involved in the SRB stuff).

however, the mainframe hardware program call stuff is a mechanism that is analogous to an application making an internal call to a subroutine library ... that just happens to be in another virtual address space (and doesn't require kernel checking about resource allocation, etc). The end of the subroutine library then has (slightly elevated) privileges to address back into the calling application's address space.

various past gnosis-keykos postings.

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