bdb@cl.cam.ac.uk (Brian Brunswick) (03/22/90)
Ok folks, there has been a lot of discussion over the troubles caused by apple because of AMAX and the software only pirated versions of it. I have a major problem to add to this debate: For a long time now (over two years) I have been toying off and on with my own version of a mac emulator - it has had no influence from AMAX, which I have never seen, and indeed was started when I had only heard of the one for the atari. It has the following properties: * Runs entire mac system (multifinder optionally) as ONE amiga task in its own screen - so rest of amiga system continues - though mac system does busy-wait and so must be at a low priority * Uses trick of displaying single bit plane mac screen together with itself shifted down one line and using a pallette to blur the two together to virtually eliminate interlace flicker. * Runs mac filing system on ANY amiga volume that you have described by mounting it - hard disks and ram disks included. I have also managed to trick real macs into using the 5MB partition of my 20MB SCSI hard disk that is currently in mac filing system format * Also has my own special mac filing system that interfaces to amigados and so accesses existing amigados volumes. * Runs by copying macplus roms into ram and patching them (Is this legal?) * Needs either: ram at 4MB point to put roms in and ram below this - mac system seems to break if ram above rom or: hardware to generate an address error at 4MB point - trivial hack of a 74LS138 and a diode - and a 68010 or better for the necessary ability to restart instructions - this is what I use. * Comfortably gives a mac 1MB smaller in size than the amiga memory - though I believe it could go up to only .5MB smaller. * Reliability is about alpha right now.. it runs system 6 multifinder and all things I've tried that are not copy protected, but crashes spontaneously sometimes. QUESTIONS Is this legal? Should I release this into the public domain - as I would like to do? (Get your own mac roms and system should go without saying) Would it be more legal if I avoided having the mac roms in ram - this would be possible, but irritating, and they would have to be at 4MB point - bending autoconfig guildlines? Don't worry - I am not about to mangle the reputation of the amiga without a lot of thought - but I would like your collective wisdom on this subject. Personal mail I will periodically post summaries of UNLESS IT SAYS NOT TO. Your opinions are invited.... Technical notes =============== I get the low memory workspace needed for the mac by rebooting the amiga system with execbase at $1400+. The mac system can be persuaded not to trash the exception vectors, but best protection is afforded by using a 68010 or better and VBR to move them out of harms way. The mac system writes directly onto the bitmap of the amiga screen - which I persuade intuition not to trash by whatever flag bit it was. Screen size matches workbench - may be morerowed or whatever. It simulates 68000 supervisor mode using 68010 user mode and a priv error handler. Mouse movement is stolen from intuition by a handler enabled when the mac screen is active, disabled by using the right button, which brings back intuition pointer for use in dragging screen/clicking it to back. Disk access goes through trackdisk.device/harddisk.device or whatever Makes floppies agonisingly slow, though hard disk is ok. I have not experimented with connecting a mac expansion drive up, though that should be possible with a home made hardware hack - I have had some experiance with reading different disk formats. Brian Brunswick, bdb@uk.ac.cam.cl, bdb10@uk.ac.cam.phx. Short .sig rules!
tron1@tronsbox.UUCP (HIM) (03/25/90)
>Item: 6159 by *Masked* at cl.cam.ac.uk >Author: [Brian Brunswick] > Subj: A PD mac emulator??? > Keyw: MAC EMULATOR AMAX LEGAL QUESTION >* Runs by copying macplus roms into ram and patching them (Is this legal?) This is PERFECTLY legal provided that your users have to PURCHASE FROM APPLE , one set of the ROMS's for every machine that will run your software (ala AMAX) >Is this legal? YEs. > >Should I release this into the public domain - as I would like to do? >(Get your own mac roms and system should go without saying) SELL IT -- if it does what you say , a $150 price would be perfectly in line. (I would love to say make it PD , but if >I< had written it I'd sell it ) > >Would it be more legal if I avoided having the mac roms in ram - this >would be possible, but irritating, and they would have to be at 4MB point - >bending autoconfig guildlines? No , no more legal at all. As long as the are loaded into ram from PHYSICAL chips (not a floppy file) you are fine. **************************************************************************** Air Traffic Controller's Bizarre Claim: "East German Whiz Kids Planted Mind C ontrol. Everything I say is Copr. 1990, except the stuff I stole from someone else and the stuff I don't want responsibility for. Kenneth J. Jamieson: Xanadu Enterprises Inc. "Professional Amiga Software" UUCP: tron1@tronsbox.UUCP BEST PATH ---> uunet!tronsbox!tron1 Sysop, Romantic Encounters BBS - (201)759-8450 / (201)759-8568 ****************************************************************************