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Old 03 March 2015, 10:31   #1
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Kickstart visible at f00000?

I am trying to understand the booting of an Amiga and looked into the Kickstart-ROM. (A1200, 3.1ROM) Of course I have a compehension problem right at the beginning ;-)

At the very beginning it calculates a checksum and then does a

; this is address f800f2 in A1200 OS3.1

LEA    ($F00000).L,A1
CMPA.L    A0,A1                ; What is compared here???
BEQ.B    .StartedFrom_f00000  ;we did start from f00000??? is that possible?
CMPI.W    #$1111,(A1)
BNE.B    .StartedFrom_f00000
JMP    (2,A1)                 ;f00000 begins with $1111. Jump ($f00002)
My question is, is the Kickstart also visible at f00000? Or when could that be the case?
I thought f00000 is Debug-ROM Space or FlashROM or used by 68060 cards?

Where does the Kickstart show up and under which circumstances/Amiga models?

Best regards
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Old 03 March 2015, 11:53   #2
Toni Wilen
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CDTV and I think it was also used by development/prototype hardware.
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Old 04 March 2015, 20:21   #3
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I think the reason for Kickstart checking whether it's running from address $F00000 is in part due to Commodore's build process.

The memory at $F00000 was originally designed/intended for ROM cartridges. That's why Kickstart checks for a signature word at $F00000 ($1111) and jumps to $F00002 if found: it's calling the ROM cartridge code.

Commodore did provide builds of Kickstart assembled for address $F00000 to developers. With those, having code to check whether it's running at $F00000 makes sense; you can't call ROM cartridge code then. The check code was left in place for Kickstarts built for other addresses, though it isn't needed then.

[Probably various RAM boards for the A1000 and possibly also the 512KB CPU-slot RAM board in German-designed A2000s can be configured to appear at $F00000.]
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Old 29 October 2018, 14:10   #4
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Kickstart visible at f00000?

It looks like it needs to match the tag at the start of your main ROM? Does that vary?

Actually no. I’m wrong.
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Old 29 October 2018, 15:01   #5
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IIRC CD32 extended ROM is also located at F00000

There's also games checking for cartrdiges at F00000 (pinball dreams).
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Old 29 October 2018, 15:02   #6
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Originally Posted by jotd View Post
IIRC CD32 extended ROM is also located at F00000

There's also games checking for cartrdiges at F00000 (pinball dreams).

Yeah I just misread the code
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Old 28 December 2018, 14:23   #7
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The custom made "GB A1000" has flash memory mapped at 0x00F00000 that does exactly this. It starts with $1111 and then has code which performs early startup code to configure 32bit memory space, plays a startup animation and then proceeds to kickstart at 0x00F80000.

[EDIT] Oops, sorry, just realised I'm posting to an old thread
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