Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!uunet!cbmvax!valentin From: valentin@cbmvax.commodore.com (Valentin Pepelea) Newsgroups: comp.sys.amiga.hardware Subject: Re: A1000 Kickstart Questions (for 2.0 hardware hack) Message-ID: <13715@cbmvax.commodore.com> Date: 9 Aug 90 02:49:19 GMT References: <90210.130137LEEK@QUCDN.BITNET> Reply-To: valentin@cbmvax (Valentin Pepelea) Organization: Commodore, West Chester, PA Lines: 41 In article jraja@niksula.hut.fi (Jarno Rajahalme) writes: > > Write protection is disabled as an consequence of the RESET command. > RESET also disables all CHIP-RAM. And all external devices. In other words, all FAST ram also. :-( > I disassembled the Boot-ROM a little and noticed that Write-Protection > is enabled by attempting to write to Boot-ROM's area. Not quite. The boot-ROM's are turned off and CHIP ram is turned on by clearing the least significant bit of the ciaa.pra register ($bfe001). But before doing that, one must first set the the least significant bit as output. We do that by setting the least significant bit of the ciaa.ddra register. ($bfe201) The following sequence will do what you want: move.b #3,$bfe201 ; Set 2 least significant bits as outputs move.b #2,$bfe001 ; Light up led; turn off boot-ROMs > Another solution would be to let the 1.3 boot normally, and then write > a program to load 2.0. There are few problems with this: > > - RESET disables the chip-RAM. So some FAST is needed. > - Would C-A-A-reset work normally??? This has indeed been done. The above code which turns on CHIP ram is first loaded into a 68020's cache, then a reset is executed, and finally the code from the cache is executed. Both SetCPU 1.6 and a special program called MMUkick do just that. Actually, since there was a 68030 accelerator board that disabled all caching of CHIP ram, even instruction caching, the cache had to be loaded from FAST ram. Quite a hack. But I've already described at length how that was done. Valentin -- The Goddess of democracy? "The tyrants Name: Valentin Pepelea may distroy a statue, but they cannot Phone: (215) 431-9327 kill a god." UseNet: cbmvax!valentin@uunet.uu.net - Ancient Chinese Proverb Claimer: I not Commodore spokesman be