Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!rutgers!cbmvax!daveh From: daveh@cbmvax.commodore.com (Dave Haynie) Newsgroups: comp.sys.amiga.hardware Subject: Re: IBM cards in the Amiga Message-ID: <13381@cbmvax.commodore.com> Date: 23 Jul 90 21:59:16 GMT References: <1990Jul20.172301.6908@watdragon.waterloo.edu> Reply-To: daveh@cbmvax (Dave Haynie) Distribution: comp Organization: Commodore, West Chester, PA Lines: 118 In article <1990Jul20.172301.6908@watdragon.waterloo.edu> rbharding@trillium.uwaterloo.ca (Ron Harding) writes: >If CBM made a 286- or 386-based board with at least EGA graphics, things >might be different... They do make a '286 board, but it's not supporting EGA display modes, only MDA or CGA, at present. Of course, it seems to me that you're far more concerned with using these free network cards than what kind, if any, MS-DOS machine you wind up with. So a cheap enough Bridge Card would serve your stated purpose. Of course, that Bridge Card, or whatever solution you come up with, should cost less than the Commodore-Amiga Arcnet or Ethernet card you could buy instead. > What we are thinking of is a bus-adapter board which uses the >Bridgeboard slot to connect the IBM slots to the Zorro bus. The primary >function of this board would be to map the IBM bus's 1Meg memory space >into one of the many unused Megs of the Zorro address range. It would >also have to map the IBM's 64K io space into another Zorro range. That's something we've been proposing for years. It's called a "dumb" bridge card; basically just a bus translator to go between Amiga and PC/AT. No one has yet publically admitted to having built one, but it could certainly be done. >Which ranges of the Zorro space are used could be set by switches, or maybe >even Autoconfig. If you're building something to go in the 3000, it had BETTER be autoconfig; some of the "tricks" you could get away with on the 2000 bus are no longer possible. > We have not resolved some issues yet. Unfortunately, the Amiga Hardware >Reference does not describe either Zorro or the 1000's expansion slot >($%#^#%@%#!!). Unfortunately, the first edition of the Hardware Reference Manual was done before they had finished the Zorro specifications. You can order these from CATS today; currently the best book for Zorro II is the "A500/A2000 Technical Reference Manual". Zorro III specifications are much more complete, but I don't think they quite have a handy book for that just yet. > - The IBM bus provides 6 or so interrupt request lines. We're pretty > sure that it would not be hard to use switches to map the IBM's 6 IRQ > (or at least the ones that are in use) lines to some unused Zorro > interrupt request lines. PC-bus interrupt lines can't be shared. So the simplest thing you could do is wire-OR them together onto one of the Amiga lines. A single 74LS05 could do this for you. > - The IBM bus provides 3 DMA channels. Is it possible to map these to > Amiga DMA channels just like the interrupts? DMA is not essential > for most IBM cards anyway, but wouldn't hurt. IBM DMA channels aren't real DMA like the Amiga, just control lines for the DMA controller on the PC. You could probably put such a DMA controller on this card; even give it access to both the Amiga and PC buses. A cheap 16 bit microcomputer might be able to do the job more flexibly. > - Many cards for the IBM PC are very slow. The Nestar is probably one > of them. In fact, some original PC cards are so slow that they won't > even work in an AT, since the shortsighted designers of them didn't > give the option to generate wait-states. It was actually IBM who was short sighted. They never wrote a specification for the IBM PC bus. So designers building cards for this bus never had a clue that some day IBM would run it much faster and expect everything to still work. If I cranked up the Zorro II bus to 10 or 12MHz from its current 7.09/7.16 specification, you would see all kinds of stuff break. Proper expansion buses include specifications that tell you exactly what to expect in any legal backplane. Any machine with a CPU faster than the bus must compensate for this, not the other way around. You can find examples of this done correctly in the Amiga 3000 or any Mac II. > We don't plan on using any hard-disk controller boards, so blazing > performance is not a concern. It should be acceptable to have the > bus-adapter automatically throw some switch-selectable number of > wait-states into every IBM bus access. That's certainly possible, and a good idea. However, be careful with it; these wait states could unduely drag down your machine's performance. A card with too many wait states can time out the bus on the A3000. > > - Any IBM cards we will be concerned with are 8-bit. The 68030 seems to > have special instructions for dealing with 8-bit peripherals ( the > MOVEP instruction, for example). I don't remember offhand whether or > not the IBM slots in the 2000 or 3000 are 16-bit long-slots or not. If > so, then there may be special challenges. The PC slots in the A3000 are AT-style slots. The 68030 does have some special instructions for dealing with peripherals like this, as I recall. But the Zorro II bus is in fact a 16 bit bus; it doesn't dynamically resize like the 68030 bus. So if you're planning to treat the PC bus space as contiguous memory, you'll have to do 8->16 and 16->8 bit funneling when necessary to map the whole thing as 16 bit memory. This shouldn't be very difficult to do. > Just imagine the possibilities if this is do-able! There are quadrillions >of cards for the IBM PC in the world. There are only a handful of Zorro >cards. With this card, you could have internal modem cards, fax modems, >extra video cards (VGA or whatever), any network card (Ethernet, Token- >ring, Arcnet, etc), A/Ds and D/As. Actually, I think you can get everything you mention, except for VGA cards and token ring networks, for Amigas now anyway (OK, the only FAX attachment I know of goes via RS-232). But there certainly are quite a few good IBM cards out there. This has at least the potential of ASDG's Twin-X card, probably more potential if it also works in an A2000 (eg, more PC slots available). I've been a fan of this idea for years, and think it has definite commercial potential, expecially if whomever builds it can write some Amiga device drivers for some of the more popular PC plugins. >Ron Harding | Nuke'Em: Get them before they get you! -- Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy The Dave Haynie branch of the New Zealand Fan Club