On October 12, 2017 at 19:56 jfmezei_nanog@vaxination.ca (Jean-Francois Mezei) wrote:
back in the arly 1990s, Tandem had a computer called "Cyclone". (these were mission critical, fault tolerant machines).
ok old fart stories...tho maybe current. IBM's big mainframes would repeat calculations as a way to detect hardware errors. Above a certain temperature they would do more repeating. If there was any disagreement it would be reported and they had some complex statistical formula to determine how many repetitions to try next and what to accept. I assume this was analogous to the various time sync game theoretic formulas to decide which time reference to believe when they conflict. It's not as simple as majority vote, the majority could be wrong (e.g., same stuck bit.) So, at least as it was explained to me, as it got warmer (e.g., A/C failure) the machine would get slower and slower, potentially to a crawl. And there was no doubt a point at which it'd just shut itself off, but before it got there. Since many mainframes were mission critical they were trying to avoid that. That was the kind of thing which made multi-million dollar mainframes cost multi-millions of dollars. Also, the IBM 3090 at least, was cooled via helium-filled pipes kind of like today's liquid cooled systems. It was full of plumbing. If you opened it up some chips were right on copper junction boxes (maybe they were just sensors but it looked cool.) There was always something amusing back then when an IBM service person would show up with one of those typical gas tanks on wheels, like one uses for welding, to top off your mainframe. -- -Barry Shein Software Tool & Die | bzs@TheWorld.com | http://www.TheWorld.com Purveyors to the Trade | Voice: +1 617-STD-WRLD | 800-THE-WRLD The World: Since 1989 | A Public Information Utility | *oo*