🚀 go-pugleaf

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
-- 
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