Custom OS4.1 kickstart ROM?

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Custom OS4.1 kickstart ROM?

Postby esc » Mon Oct 26, 2015 12:06 pm

Hey guys,

First post here. New to the OS4.1 scene. :)

I like burning custom kickstart ROMs for my Amigas. With a Romy modification on my A4000, I can use a 1MB Kickstart ROM. I was wondering, is it possible to create one specifically for OS4.1 Classic FE? What are the list of the ROM components that are loaded into memory from disk after the initial boot of the Amiga?

Thanks!
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Re: Custom OS4.1 kickstart ROM?

Postby ZeroG » Mon Oct 26, 2015 12:42 pm

esc wrote:I like burning custom kickstart ROMs for my Amigas. With a Romy modification on my A4000, I can use a 1MB Kickstart ROM. I was wondering, is it possible to create one specifically for OS4.1 Classic FE?

No, 1MB is way to small.

What are the list of the ROM components that are loaded into memory from disk after the initial boot of the Amiga?

The stuff in SYS:Kickstart/ or to be more correct the things that are listed in SYS:Kickstart/Kicklayout.
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Re: Custom OS4.1 kickstart ROM?

Postby tonyw » Mon Oct 26, 2015 2:54 pm

The Kickstart ROM is 68K code, while AmigaOS is all PPC code. Part of the boot process that runs on the 68K CPU is to switch on the PPC processor and boot it from the system volume. That process has to be loaded and run by the 68K CPU, which switches itself off once the PPC processor is running.
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Re: Custom OS4.1 kickstart ROM?

Postby esc » Mon Oct 26, 2015 3:38 pm

Hm, so would it be possible to load all the 68k stuff into a custom Kickstart ROM, just the things that are needed to transition from the 68k boot process into PPC mode?
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Re: Custom OS4.1 kickstart ROM?

Postby tonyw » Tue Oct 27, 2015 12:06 am

Possibly. You would need to identify which 68K modules you could remove, before you reused their space with the "hand-over" components.

I must admit I know nothing about the process, having never owned a PPC accelerator for my 4000. You would have to ask one of the devs that was involved with the Classic installation. Perhaps DarrenHD could help you?
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Re: Custom OS4.1 kickstart ROM?

Postby alekc » Tue Oct 27, 2015 1:19 am

What we would gain having such custom ROM? I'm sorry but looking at current OS4.1 architecture and the fact that 68K gets turned off pretty quickly during boot phase I fail to see any real advantages or am I missing something? However it sounds like an interesting "hacking" project for long winter evenings.
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Re: Custom OS4.1 kickstart ROM?

Postby esc » Tue Oct 27, 2015 12:42 pm

alekc wrote:What we would gain having such custom ROM? I'm sorry but looking at current OS4.1 architecture and the fact that 68K gets turned off pretty quickly during boot phase I fail to see any real advantages or am I missing something? However it sounds like an interesting "hacking" project for long winter evenings.


Precisely this. Plus it helps me wrap my head around what's going on "under the hood" so to speak. :)
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Re: Custom OS4.1 kickstart ROM?

Postby alekc » Tue Oct 27, 2015 2:48 pm

Thanks for explanation esc and goodluck with your project. Sounds really interesting. There are developers on the board who have enormous knowledge about AOS4.1 on classic hardware. Hope they can help you.
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Re: Custom OS4.1 kickstart ROM?

Postby DarrenHD » Mon Dec 14, 2015 7:00 pm

esc wrote:Hey guys,

First post here. New to the OS4.1 scene. :)

I like burning custom kickstart ROMs for my Amigas. With a Romy modification on my A4000, I can use a 1MB Kickstart ROM. I was wondering, is it possible to create one specifically for OS4.1 Classic FE? What are the list of the ROM components that are loaded into memory from disk after the initial boot of the Amiga?

Thanks!


We thought about this early on, and to use something like the Deneb which has a flash-rom that can survive the OS4 reboot process, but there wasn't enough space on the Deneb's rom to hold all of the OS 4.x kickstart.
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