Date: Sun, 3 Oct 2004 11:21:14 -0700 (PDT) From: "Bruce R. Montague" <brucem@mail.cruzio.com> To: andrea@webcom.it Cc: durham@jcdurham.com Subject: Re: Sudden Reboots Message-ID: <200410031821.i93ILEro000360@mail.cruzio.com>
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Hi, Andrea, regarding inverted page tables: > Actually, all Power and PowerPC chips have this... Thanks for pointing that out. I believe the entire line of IBM virtual memory hardware that supports IBM's form of "inverted page tables" is all directly related, if not the same, and descends from the never-completed 1970s-era IBM "Future System" (FS) project. Or perhaps it was a version redone for the System/38 that used lessons learned from the FS? Is this right? The AS/400 has successfully used this architecture for a long time. Most of the other systems that have used this architecture (RT, RS) seem to have never quite caught on. Is this VM unit and the Power/PowerPC's the same? They "cheat" a bit with a hash table to keep the cost of the associative memory down; perhaps increasing its size is the natural evolution of this VM architecture? Are there any "true" single-level store OSes running on this inverted PT hardware? (That is, where RAM is literally treated as just an "invisible" performance cache for a secondary-storage primary memory.) I assume the OS/400 is, but maybe an expert knows for sure? OS/400 runs on modern AS/400's which use the PowerPC, unless I'm mistaken... Sorry to have so many questions and no answers, hopefully the coffee will kick in soon. The FS apparently was IBM's biggest failure; some say it had a lot to do with the growth of silicon valley. A history of the IBM "Future System" and the technologies it spawned would be very interesting. There seems to be little info on it around: www.cs.clemson.edu/~mark/fs.html - bruce
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