Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!think.com!zaphod.mps.ohio-state.edu!cis.ohio-state.edu!ucbvax!AUVM.AUVM.EDU!JIM From: JIM@AUVM.AUVM.EDU (Jim McIntosh) Newsgroups: comp.lang.asm370 Subject: Re: disabling CTRL-BREAK (dos) Message-ID: <9105260449.AA16148@ucbvax.Berkeley.EDU> Date: 26 May 91 04:28:10 GMT Sender: daemon@ucbvax.BERKELEY.EDU Reply-To: IBM 370 Assembly Programming Discussion List Distribution: inet Organization: The Internet Lines: 31 In article <910524.224442.EDT.VALDIS@vtvm1.cc.vt.edu>, Valdis Kletnieks says: >Does anybody out there have a war story of a "undocumented" opcode or >similar feature on an IBM 360/370/etc mainframe? Well, this is probably more appropriate for the alt.computer.folklore newsgroup, but here goes. Back in the early 80's I worked for a small PCM called Magnuson. The Magnuson processor had been designed by Carl Amdahl (which meant our company was called "Son of Amdahl") and competed with the 138/148 (and later the 4331/4341) boxes. The guy who wrote the initial cut of the microcode was a guy named Kevin Anderson (still in jail, last I heard, for trying to ship things he shouldn't have to the Russians). Kevin was an Othello buff, and hacked a game we had on our games disk... moving critical routines into the microcode. The Magnuson M80 was, therefore, the only IBM 370-compatible machine that had (in addition to ECPS:MVS, ECPS:VM, etc.) an undocumented ECPS:OTHELLO. I pity the poor programmer who stumbled into that instruction. :-) Speaking of assembler trivia, what are the three 370/390 instructions that have to be done twice in microcode for each target instruction? (The microcode has to run through the whole operation once to see what will happen, and then again for real.) Hint: The answer's in the POO. :-) --- Jim McIntosh (jim@auvm.auvm.edu) The American University Washington DC 20016-8019 USA