Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!mailrus!sharkey!itivax!scs From: scs@itivax.iti.org (Steve Simmons) Newsgroups: comp.mail.elm Subject: Re: Serious elm problems on Sun OS 3.5.2 Message-ID: <2822@itivax.iti.org> Date: 16 Aug 89 18:24:08 GMT References: <2311@oakhill.UUCP> Distribution: usa Organization: Industrial Technology Institute, Ann Arbor, MI. Lines: 36 mikes@oakhill.UUCP (Mike Schultz) writes: >But then it happened to me one day and I could repeat the failure, so I got out >adb and went bug hunting! And what did I find? I found an illegal instruction >in the middle of the object file. No, I didn't disassemble in the middle of >an instruction, it was right there in the middle of the disassembly of the >legal instructions,.... And then it wasn't! >Yes, that's right. While poking around trying to figure out how on a virtual >memory machine with page protection, elm managed to get an instruction trashed, >the instruction fixed itself and elm ran my test case without failure! >Whoa! I took my evidence to the system managers . . . And they said "You're crazy". We had the same thing happen (tho not with elm) at another site where *I* was the system manager -- Suns, and certian programs would random crash with illegal instructions. Only certian programs. And relinking a new version would make the problem go away. The programmers complained to the system manager (me) and I said they were crazy. They weren't. It turns out that there is a hardware bug in some Sun 3/50s (those made before 1988, I think). It affects very very few programs, and requires some really odd circumstances -- a branch instruction at the end of a virtual page which crosses into the 'next' page, which causes a page fault, and other I/O must be happening at the same time (I'm serious!) and sometimes it'll happen. So: do you have old 3/50s? Does the problem occur only there? Does it come and go as versions of elm change? If so, you been bit. -- Steve Simmons scs@vax3.iti.org Industrial Technology Institute Ann Arbor, MI. "Velveeta -- the Spam of Cheeses!" -- Uncle Bonsai