cclist wrote: On 1/16/2006 at 7:44 PM Philipp Hachtmann wrote: IIRC, it was indeed a problem on the CDC 7600 PPU's. A very tight (e.g., UJN 0) loop would cause core to overheat. The 7600 added a duty-cycle integrator so that repeated accesses to the same location in a short amount of time would actually slow things down a bit to avoid that problem. But the 7600 was a very fast machine for its time. Cheers, Chuck Okay, Two points. Halt and Catch Fire was a fictious command. This was sort of an in-group joke. I first saw them described when the IBM 360 was announced in 1963. But they were already old at that time. I came across one of the lists a few months ago in a clean up. Others included: Read and Stretch Tape; Read Card and Shred; Seek Disk and Crash; Print Line and Jam Paper (w./ a variation of Print and Tear Ribbon); Type Wrong Character; Jump To Illegal Address; etc. You can probably create your own. In fact Datamation ran a humor article and asked for creative commands. They published some of the best ones. Any old timer refers to this class of humour as Halt and Catch Fire, since it was usually first on the list. My favorite was Execute and Hang, since it happened often in CDC 3000 machines. We called them Blue Sky commands since the machine went into an undefined state. I'll bet that some of the other old timers better organized than I, still have those lists and will reply with them. Second point. I worked on a lot of 7600s. And I was on the team that designed the Cyber 17X replacements. I never heard of one catching fire. The core ran at 27.5ns cycle time (actually, that was when the data was available - you still had to restore it, since core read out switched the state of the core). That was fastest that core ever was used in a commercial product. At least we advertised it that way. But, if you have a 7600 logic module, look at it closely. The modules is aluminum heat sink on 5 sides - the connector is on the 6th side. It screwed into a solid "cold bar" that had Freon piped through it. There were "cold plates" inserted between modules. All of this removed the heat from the module quickly. The PCBs are actually in a miniature refrigerator. The circuits had thermal compensation built in for the memory modules. Seymour had thought of tight loops and used them to test memory during design. Many of the field memory tests were coded to as tight as possible to stress the memory. Halt and Catch fire was a joke. I never heard of 7600 catching fire. We had a chassis melt once, when the refrigeration stopped and the fail safes all failed. But no fires. Billy