All normal Amiga ROMs start with the following: I inspected the hex dump of the first few bytes of the CDTV ROM. (Footnote: interestingly, the code for these two items has been in Kickstart since version 1.2 if not earlier, and seems to be in as late as 3.1 - meaning that if there's a way to get a ROM with the right magic number to appear at 0xf00000, just about any Amiga will run it!) The CDTV extended ROM

the entire area from 0xf00000 to 0xffffff is scanned for ROMTags.exec, normally mapped at 0xf80000, will very early in the process see if there's another ROM at 0xf00000, and jump to it if it appears to be valid.In particular, it confirms points 1 and 2 in pndc's answer: The commented disassembly of Exec by Markus Wandel provides some very useful information. Firstly it seems that CDTV and CD32 do things slightly differently so I'll examine them separately. With the information in pndc's answer to this question I've been able to examine the various ROMs and I think I have the definitive answer. How do these ROMs 'wedge' into the regular Kickstart ROM and cause some of its functionality to change? For example, both replace the 'insert disk' screen with an animated CD screen, and of course integrate drivers for the CD-ROM drive.Is the ROM overlay different on the CDTV/CD32? (On normal Amigas, the ROM overlay is active at power-on/reset and causes the 0xF80000 ROM to also appear at address 0).Where do these ROMs appear in the memory map?.My questions are about how these extended ROMs work. The Amiga CD32 also had an extended ROM, although I have heard (unconfirmed) that in practice it may have been two logically distinct ROMs put onto the same physical ROM IC. The CDTV-specific code wedges into the Kickstart 1.3 ROMs and executes on startup.

The CDTV uses a standard 16-bit Kickstart 1.3 ROM in socket U13, exactly the same as the ROM in a 2000 or 500, with an additional pair of 8-bit EPROMs in sockets U34 and U35 containing the CDTV-specific code such as the audio player and the CD-ROM filesystem. The Commodore CDTV contained a normal Kickstart 1.3 ROM, plus an 'extended ROM'. Continuing my series of questions about Amiga ROMs :-)

Kickstart 1.3 rom download