mwandel@tiger.waterloo.edu (Markus Wandel) (04/10/90)
[Line eater: Do you know why nobody ever responds to my postings? I don't...] This may sound like a dumb question but bear with me. How do you kickstart an A1000 off something other than its internal floppy drive? The reason I ask is that a hard disk interface made by Comspec for the A1000 actually kickstarted off the hard disk, so it must be possible. I don't have such an interface and they are not made any more, but a friend who has used one reports that it attached to an otherwise unmodified A1000. Thus there must be a "hook" somewhere in the A1000's boot ROM which allows an external box to take control and dump in the kickstart data before it gets read off floppy. Maybe some prehistoric "cartridge port" scheme? I'm running a homebrew hard disk interface anyway, so if it's just a matter of "place a ROM at this address and have such and such a signature in it", I would happily build whatever hardware required to make it work. I'm aware that a commented disassembly of the A1000 boot ROM exists and has been published, but I've never seen it. Could someone who has this book, or (I barely dare hope) someone at Commodore or Comspec who knows the trick enlighten me? I've already cooked up an autoboot scheme; I'd *love* to be able to start up my machine without any floppy disk access at all. I don't want to put in a ROM adapter just yet. Barring the above, is it possible to somehow disable the boot ROMs in the A1000 immediately after reset (via the OVL* line perhaps) and have the 68000 actually bootstrap out of external ROM? Markus Wandel mwandel@tiger.waterloo.edu (519) 884-9547
valentin@cbmvax.commodore.com (Valentin Pepelea) (04/10/90)
In article <23080@watdragon.waterloo.edu> mwandel@tiger.waterloo.edu (Markus Wandel) writes: > > [Line eater: Do you know why nobody ever responds to my postings? I don't...] The questions that you ask are always about boot up code, and the specialist on that subject is Bryce. Unfortunately he does not have time to read and post on this newsgroup. > Barring the above, is it possible to somehow disable the boot ROMs in the > A1000 immediately after reset (via the OVL* line perhaps) and have the 68000 > actually bootstrap out of external ROM? SetCpu 1.5 permits MMU equipped Amigas to boot off a kickstart file. The trick to that is to execute a RESET instruction and then continue execution out of the instruction cache. The commands in the instruction cache then disables the ROM from being seen at address 0+ and execution continues out of CHIP ram. Take a look at Dave Haynie's code, you'll learn something. You can probably use the same trick for 68000 equipped Amigas. Load up the following code to be executed in CHIP ram: CHIPcode: move.l 4,a6 ; Get Execbase lea.l Poof,a5 ; Code to execute in supervisor mode jsr Supervisor(a6) CNOP 0,4 Poof: move.b #3,$bfe201 ; Set up read/write bits reset ; Poof! move.b #2,$bfe001 ; Turn off ROM from location 0 cont ; Continue with this intruction I'm not sure this code would work, because the $bfe201 register might get reset after the reset instruction. The alignement for the instruction prefetch might also be wrong. 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
rbabel@babylon.UUCP (Ralph Babel) (04/11/90)
In article <10741@cbmvax.commodore.com> valentin@cbmvax.commodore.com (Valentin Pepelea) writes: > I'm not sure this code would work, because the $bfe201 > register might get reset after the reset instruction. Yup, all port pins will be set to input after RESET. Ralph ...!{cbmvax|nccnet}!cbmehq!babylon!rbabel