Article View: comp.arch
Article #1698Re: Registers in memory
From: Bob Clements
Date: Sat, 29 Jul 1989 15:56
Date: Sat, 29 Jul 1989 15:56
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From article <8907281547.AA28878@maxwell.ece.cmu.edu>, by mbjr@maxwell.ece.cmu.edu (Mauricio Breternitz): > The (now ancient) IBM 1130 also had the three index registers > at memory locations 1, 2, 3 The not-quite-so-ancient-as-an-1130 DEC PDP-5 had the Program Counter in core memory, at location zero. The bootstrap loader (which read programs at 110 BPS from the reader of the Model 33 TTY) used this feature to transfer to the newly loaded program. Just read a datum into location zero, and suddenly you were no longer running in the bootstrap. The PDP-8, largely compatible with the PDP-5, had its PC in flipflops. So the bootstrap had to recognize stores to zero and treat them as jumps. /Rcc Bob Clements, K1BC, clements@bbn.com
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Path: arc1-ca.pugleaf.net!utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!bbn!bbn.com!clements From: clements@bbn.com (Bob Clements) Newsgroups: comp.arch Subject: Re: Registers in memory Message-ID: <43492@bbn.COM> Date: 29 Jul 89 15:56:39 GMT References: <8907281547.AA28878@maxwell.ece.cmu.edu> <3602@csd4.milw.wisc.edu> Sender: news@bbn.COM Reply-To: clements@BBN.COM (Bob Clements) Organization: Once DEC, but not recently! Lines: 18