Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!rutgers!cbmvax!daveh From: daveh@cbmvax.commodore.com (Dave Haynie) Newsgroups: comp.sys.amiga.emulations Subject: Re: NeXT emulation? Message-ID: <20877@cbmvax.commodore.com> Date: 23 Apr 91 14:58:09 GMT References: <91108.003225JBK4@psuvm.psu.edu> Reply-To: daveh@cbmvax.commodore.com (Dave Haynie) Organization: Commodore, West Chester, PA Lines: 91 In article holgerl@amiux.UUCP (Holger Lubitz) writes: >In article <91108.003225JBK4@psuvm.psu.edu> JBK4@psuvm.psu.edu writes: >>Seeing that the Amiga list of emulators keeps growing I was wondering if there >>is anyone out there developing a NeXT emulator for the Ami. Or does one alread >>y exist? Running the NeXT Operating System on an Amiga would be similar to running the Mac OS on an Amiga. That's mainly an operating systems port, not an emulator. In the case of the Mac OS, what I call a "hostile port", since it was done without the source code or blessing of the originators of the OS. Such a thing is theoretically possible to do with an '030 based Amiga and the NeXT OS, though given the relative complexity of the NeXT OS vs. the Mac OS, it would be much more difficult. If it were typical UNIX, I'd say, difficult to the extent that no one would do it, since typical UNIX compiles much of the system specific stuff in as part of its kernel, and that's what you would have to change around. Graphics is no real problem. If NeXT really does render everything through DPS, then the display is really device independent, and could come out on an Amiga display, 2410, or the laser printer on the desk next to you equally easy with the right display drivers in place. Device Independence implies that everything is rendered in the terms of the imaging model, and programs don't have any idea about the physics of the output device (DPI, pixels, colors, etc.). >But you could try NeXTstep upon Commodores SVR4, I suppose. Commodore UNIX would be a much better choice for anyone wanting UNIX on their Amiga. NeXTStep or no NeXTStep. >What bothers me more is this: When is the NeXT going to be able to emulate our >beloved AMIGA ? Practically never... >Sure, there are the custom chips to be emulated, but after all the NeXT has >an '040 in it... Problem is, it requires more than simple CPU speed to achieve such a trick. For a history lesson, take a look at an Amiga, even a fast one, emulating the comparatively simple VIC chip in a C64 emulator. If you really attempt to have the 68040 emulate Copper instructions in realtime, for example, you need a display unit capable of taking raster interrupts and a CPU capable of servicing them quickly. Even an '040 NeXT Cube with that i860 display board they keep taking about would have its hands full doing this. Not that it can't do something more amazing, it's just that Amiga chips were not designed to be emulated in software, and won't be at all easy to emulate in software. >Speed of an emulated Amiga should be somewhat faster than a stock amiga, it >might even reach the speed of an '020-Amiga. Well, since the processors are compatible, if you threw out the NeXT OS, ran the Amiga OS on the NeXT hardware, all non-graphics operations would go about as fast as on a normal '040 based Amiga. If you kept the NeXT OS and somehow emulated the Amiga Kernel, things would slow down a bit because of the virtual machine traps and the inherent extra overhead of the NeXT OS on top of the Amiga OS. It's impossible to tell how fast that would really go. But once any real Amiga-like graphics stuff had to happen, the NeXT would slow to a crawl (keep in mind, you also have little graphic incompatibilities, aside from chip emulation itself, like the need to convert Amiga's bitplane graphics into NeXT packed pixel graphics, in realtime, etc.). >Of course it would require a Colorstation to emulate the >color, but everything else should be possible on a normal NeXTstation. Chances are, the Color NeXTStation doesn't have the hardware hooks necessary to emulate an Amiga copper realistically. Which makes sense -- as long as DPS is the NeXT's only interface between programs and display hardware, you don't normally have a way to take advantage of copper-type operations. And with direct mapped color (even 12 bit color as on the Color NextStation), many of the copper's uses go away. You also don't have the freedom of choosing display buffers the Amiga does, though that becomes moot, since you would have to emulate the entire Amiga video subsystem in software, as mentioned above (chip registers, pixel conversions, etc). The only real chance for this to work (of course, brushing the obvious legal issues aside) would be in the future. When Amiga gets the retargetable graphics everyone's been clamoring for, running the AmigaOS on the NeXT wouldn't be so tough. You would write a graphics device driver for the NeXT hardware, or for the NeXT's DSP (which would be real slow, but would work), just like you would write disk, keyboard, port, and mouse drivers for the Amiga OS to use the other NeXT machine facilities. All in all, you'd still be better off with an Amiga in the first place, in any case. >Holger Lubitz, Kl. Drakenburger Str. 24, D-W-3070 Nienburg/Weser -- Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy "That's me in the corner, that's me in the spotlight" -R.E.M.