Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!srcsip!haarlem!shankar From: shankar@haarlem.SRC.Honeywell.COM (Son of Knuth) Newsgroups: comp.sys.apple Subject: Re: multitasking, softswitch, etc. Message-ID: <19611@srcsip.UUCP> Date: 30 Mar 89 19:09:47 GMT References: <8903181259.aa27052@SMOKE.BRL.MIL> <10183@bloom-beacon.MIT.EDU> <9949@smoke.BRL.MIL> Sender: news@src.honeywell.COM Reply-To: shankar@haarlem.UUCP (Son of Knuth) Organization: Honeywell Systems & Research Center, Camden, MN Lines: 20 In article <9949@smoke.BRL.MIL> gwyn@brl.arpa (Doug Gwyn (VLD/VMB) ) writes: > >The only serious problem with multitasking the IIGS (in 16-bit mode) >is that a context switch involves saving quite a bit of state, for >example the direct page. The lack of memory protection is a nuisance >only if tasks run amok; so long as they are well-behaved the ToolBox >memory management should suffice. I don't follow - I would consider context switching one of the strengths of the 65816. Basically, just change the direct page register, and forget about saving the direct page contents. Right off hand, I think the only time this would be a problem is with non-well-behaved programs, were well-behaved is defined as accessing bank 0 using only stack or direct page addressing modes (i.e. not using regular or long addressing with bank 0). --- Subash Shankar Honeywell Systems & Research Center voice: (612) 782 7558 US Snail: 3660 Technology Dr., Minneapolis, MN 55418 shankar@src.honeywell.com srcsip!shankar