The shop I worked at in the late 70s had an Amdahl box. Don't remember the model; it was red, if that helps. The newest version of MVS came with a test early in NIP to check for supported hardware. It executed an instruction that our Amdahl box did not have in its arsenal. On our machine, this would cause a S0C1. There were other 'new' instructions in the OS as well, rendering the box pretty much useless.
Amdahl to the rescue. They gave us a software usermod that would get control for any program interrupt. If it was a S0C1, the code would check for one of the new instructions. If not one of those, the error would percolate. If it was an unsupported instruction, the Amdahl code would simulate the function provided by the missing instruction, which in some cases meant doing nothing at all. Before returning control to the mainline, the usermod would replace the original instruction in memory with either a direct branch to the simulation routine or else a NOP if there was nothing to do. Early in the IPL life, there would be lots of S0C1 interrupts, but as time went on there would be fewer and fewer as the offending instructions were replaced. It worked amazingly well. . . . J.O.Skip Robinson Southern California Edison Company Electric Dragon Team Paddler SHARE MVS Program Co-Manager 626-302-7535 Office 323-715-0595 Mobile [email protected] -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Shmuel Metz (Seymour J.) Sent: Sunday, December 28, 2014 10:27 AM To: [email protected] Subject: Re: Slushware In <84bccd71182f0046bcd2fb054fe5237917b2ee2...@hqmailsvr02.voltage.com>, on 12/27/2014 at 09:17 AM, Phil Smith <[email protected]> said: >This is fun. I'm not sure modern machines are both microcoded AND >millicoded-I thought millicode was just another form of microcode. Am I >wrong? Yes; millicode is the same as what Amdahl called macrocode, and is one level up from microcode, using (mostly) normal S/3x0 instructions. -- Shmuel (Seymour J.) Metz, SysProg and JOAT ISO position; see <http://patriot.net/~shmuel/resume/brief.html> ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
