English Amiga Board


Go Back   English Amiga Board > Support > support.Other

 
 
Thread Tools
Old 03 March 2015, 11:31   #1
selco
Registered User
 
Join Date: Aug 2013
Location: Germany
Posts: 56
Kickstart visible at f00000?

Hello,
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

Code:
  
; this is address f800f2 in A1200 OS3.1

LEA    (START,PC),A0
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
selco is offline  
Old 03 March 2015, 12:53   #2
Toni Wilen
WinUAE developer
 
Join Date: Aug 2001
Location: Hämeenlinna/Finland
Age: 43
Posts: 22,110
CDTV and I think it was also used by development/prototype hardware.
Toni Wilen is offline  
Old 04 March 2015, 21:21   #3
mark_k
Registered User
 
Join Date: Aug 2004
Location:
Posts: 2,966
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.]
mark_k is offline  
Old 29 October 2018, 15:10   #4
plasmab
Banned
plasmab's Avatar
 
Join Date: Sep 2016
Location: UK
Posts: 2,917
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.
plasmab is offline  
Old 29 October 2018, 16:01   #5
jotd
This cat is no more
jotd's Avatar
 
Join Date: Dec 2004
Location: FRANCE
Age: 47
Posts: 2,688
IIRC CD32 extended ROM is also located at F00000

There's also games checking for cartrdiges at F00000 (pinball dreams).
jotd is offline  
Old 29 October 2018, 16:02   #6
plasmab
Banned
plasmab's Avatar
 
Join Date: Sep 2016
Location: UK
Posts: 2,917
Quote:
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
plasmab is offline  
 


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Similar Threads
Thread Thread Starter Forum Replies Last Post
Any way to make ROM calls visible? pintcat support.Apps 7 26 July 2012 17:41
WB 3.0 windows out of visible screen ? Jack Burton support.Apps 2 22 March 2010 16:49
Amiga games where bullets are not visible? s2325 Retrogaming General Discussion 7 20 March 2009 14:42
ffs-partition visible but not accessible demax support.Other 5 18 March 2008 00:08
Hard drive not visible in A1200 Marcincz55 support.Hardware 6 06 December 2006 01:13

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +2. The time now is 18:23.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2018, vBulletin Solutions Inc.
Page generated in 0.09542 seconds with 13 queries