Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!pacific.mps.ohio-state.edu!linac!att!pacbell.com!tandem!zorch!amiga0!mykes From: mykes@amiga0.SF-Bay.ORG (Mike Schwartz) Newsgroups: comp.sys.amiga.advocacy Subject: Re: 8-bit death Message-ID: Date: 16 May 91 20:45:18 GMT References: <3335.tnews@templar.actrix.gen.nz> <1991May10.000135.7550@NCoast.ORG> <3636.tnews@templar.actrix.gen.nz> <1991May12.180515.20191@NCoast.ORG> Organization: Amiga makes it possible Lines: 58 In article <1991May12.180515.20191@NCoast.ORG> allbery@NCoast.ORG (Brandon S. Allbery KF8NH) writes: >As quoted from <3636.tnews@templar.actrix.gen.nz> by jbickers@templar.actrix.gen.nz (John Bickers): >+--------------- >| Quoted from <1991May10.000135.7550@NCoast.ORG> by allbery@NCoast.ORG (Brandon S. Allbery KB8JRR/AA): >| > As quoted from <3335.tnews@templar.actrix.gen.nz> by jbickers@templar.actrix.gen.nz (John Bickers): >| > | PClone, it appears to involve using fixed tables of vectors into the >| > | ROMs. >| > >| > ??? ONE interrupt is used for system calls --- INT 21H (that, by the way, is >| >| Then I must be including things akin to our external libraries. I'm >| fairly sure that I've used a different number to do things with the >| display. 0x10...? >+--------------- > >That's the BIOS viden interrupt. As I said, you're "not supposed to do that". > >+--------------- >| > be dropped into place. Theoretically, you're not supposed to call the BIOS >| > directly, but we all know what MS-Doesn't is like.... >| >| Must be it. Now that I know so many microcomputer OSes do this sort >| of thing, I'm certainly interested in _why_ they do it. >+--------------- > >Do *which* sort of thing? One interrupt for the OS entry point? > >That's probably because it potentially has even more possible values than you >have interrupts. Should MS-Doesn't ever break the 256-syscall barrier (this >is, you understand, purely theoretical :-) , they can expand the system calls >to use AX instead of AL (set AH=0 and you have the original set), thus 65536 >system calls. That's probably the limit for DOS, though, until and unless >they drop 8088 "real" mode. (Of course, AH is already used by some calls and >programmers expect AH to be unused in others, so the All-Holy Compatibility >with DOS 1.25 programs would be broken by this, so it'll never happen. :-) > >A better example: a 680x0 Unix I used which used one of the "trap" calls and >placed the system call number in d0. Now, how many possible system calls is >that? 4,294,967,296! The Unix Thought Police will get them for kernel bloat >before they get anywhere near that many syscalls. :-) *How* many interrupts >did you say you had, in comparison (even using the Mac-noid 1010/1011 trap)? > >++Brandon >-- >Me: Brandon S. Allbery Ham: KF8NH on 10m,6m,2m,220,440,1.2 >Internet: allbery@NCoast.ORG (restricted HF at present) >Delphi: ALLBERY AMPR: kf8nh.AmPR.ORG [44.70.4.88] >uunet!usenet.ins.cwru.edu!ncoast!allbery KF8NH @ WA8BXN.OH In my own homebrew portable 68000 video game OS, I implement libraries similar to the Amiga's. I load the jump tables into very LOW memory, which allows me to use jmp (addr).w (absolute short), which is quite efficient, to access my libraries. -- **************************************************** * I want games that look like Shadow of the Beast * * but play like Leisure Suit Larry. * ****************************************************