Hi, Tony,
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What I recall is, IBM PokLabs was trying hard to "kill off" the whole VM product line around that time.
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What I heard is this:
Fortunately, Tom Watson Jr. was smart enough to realize what was going on, politically, inside IBM, and so he asked the PokLabs MVS-XA developers if they could create MVS/XA without using the internal version of VM/XA, and of course, they reluctantly admitted that they could not get it done in a timely manner without VM/XA.? ?With that, Tom made an executive decision and told them to stop trying to kill VM, and figure out how to make a VM/XA product to assist IBM's customers wanting to migrate to MVS/XA.
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That is what the original VM/XA Migration Aid was all about.? No enhancements to CMS at all; it was just the barest minimum to run MVS/XA under VM, and you could run "side-by-side" with MVS/370 in one VM and MVS/XA in a second VM.? ?This was well before the arrival of LPARs.
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Eventually, it evolved into VM/XA SP, and ultimately, VM/ESA.
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Another reason for the "HCP" designation (I heard it stood for "Hypervisor Control Program") was that for "XA", IBM had invented the 370-XA mode SIE instruction, that basically had put much of "CP" into the microcode.? So, the new HCP version of "CP" in VM/XA and above was very different from the older versions of VM/370 and VM/SP or HPO that came before on the original 370 hardware (before the arrival of 370-XA mode and the SIE instruction.)
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Mark S. Waterbury
