On Tue, 1 Dec 2015 12:52:05 +0000, Bob Shannon wrote: >> Amdahl responded by shipping some code that was loaded early in IPL to >>accommodate the new instructions > >SE and SP Assist. They trapped the abend in the FLIH. I remember it well.
That's SE Assist. And it led to the design on the 580 series of computers that provided a third state of operation called (IIRC) System state. The 580 design included hardware to virtualize the user's processor. The code that ran in System state was called Macrocode and it was loaded from the console processor into memory that was outside of the memory available to customers. Macrodode routines emulated new instructions. A side benefit of all that was that it made Multiple Domain Facility possible. The hardware that supported the virtualization included additional registers for the use of Macrocode and other facilities that made MDF quite efficient. -- Tom Marchant ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
