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From: phil@adam.adelaide.edu.au (Phil Kernick)
Newsgroups: comp.sys.amiga.misc
Subject: Re: Mac emulation
Message-ID: <phil.668831862@adam.adelaide.edu.au>
Date: 13 Mar 91 02:37:42 GMT
References: <1991Mar10.142932.14676@cunixf.cc.columbia.edu> <jms.3407@vanth.UUCP> <1991Mar12.224108.822@javelin.es.com>
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pashdown@javelin.es.com (Pete Ashdown) writes:

>jms@vanth.UUCP (Jim Shaffer) writes:

>>>someone from dumping them to EPROM and using that instead?

>WRONG.  Dumping the Mac ROM image to an EPROM, then using the EPROM in the
>A-Max cart will NOT work.  The actual Mac ROMs are 'special' in some way,
>how that is, I don't know exactly.  What I understand it to be is that you
>need to strobe a location several times before they will dump their image
>to you.  The A-Max software does in fact do this and if you are using an
>EPROM copy, it will not work.

Who told you this?  It is *completely* false, at least with the 128K
ROMs.

Next time you have a chance, look at a real Mac ROM.  It is just a 64Kx8
JEDEC package ROM.  Nothing more, and nothing mysterious.

Next, have a look inside the AMax cartridge.  On opening mine I see a
handful of standard 74 series logic chips.  Consult the data book, and
it seems we have a counter on the address lines and then a parallel to
serial converter on the data lines and a bit of glue logic.  All the
cartridge does is:
        Reset the counter
        Increment the address
        Strobe out the data

Using an EPROM copy *will* work, and if Apple did not have it's
restrictive policies I would suggest that you *NOT* do this.  However,
if Apple insists on it, they will simply move the market into the grey
area and will lose money.  Seems to me they are "cutting off their nose
to spite their face".  If the company (Wombat?) that was cloning the
ROMs succeeds then this will all be moot anyway.


Phil.

-- 
o|      ///   Phil Kernick              EMail:  phil@adam.adelaide.edu.au    |o
 |     ///    Departmental Engineer     Phone:  +618 228 5914                |
o| \\\///     Dept. of Psychology       Fax:    +618 224 0464                |o
 |  \///      University of Adelaide    Mail:   GPO Box 498 Adelaide SA 5001 |