Aphs.207 net.unix-wizards utcsrgv!utzoo!decvax!ucbvax!ihnss!cbosg!harpo!chico!duke!phs!dennis Fri Jan 22 23:41:27 1982 Re: overlay loader You get the overlay stuff for free with 2.8bsd; using it I've managed to get ex3.? running on a non split I/D machine, and I'm on the verge of getting rogue running on it, too, but that's MUCH harder. It works, I've never been able to track any bugs to the overlay stuff, but I still can't figure out why vi tells me the file is incomplete whenever a search fails... As for loading of the overlays, they're always there; the EMT instruction is used to cause the kernel to fiddle with the paging registers. The loader sets up routines in low memory (the base segment) which do the EMT and call the real routine after it's been mapped in. The whole text space (including overlays) is still swapped as a unit. There are lots of ways to arrange the overlays; the maximum text space (for a split I/D machine) is 8192+7*57344 = 409600 text bytes. Of course, it's hard to get an 8K base segment (the C library wants to go there...) and there's going to be lots of overhead space for the indirection routines, but that's the ideal, anyway. ----------------------------------------------------------------- gopher://quux.org/ conversion by John Goerzen of http://communication.ucsd.edu/A-News/ This Usenet Oldnews Archive article may be copied and distributed freely, provided: 1. There is no money collected for the text(s) of the articles. 2. The following notice remains appended to each copy: The Usenet Oldnews Archive: Compilation Copyright (C) 1981, 1996 Bruce Jones, Henry Spencer, David Wiseman.