ROM format/structure question.

[Doobrey]

Does anyone know the what the last 16 bytes in the Amigas ROM is for?..
 I know 8 bytes before it is the checksum and the rom size,but I`ve drawn a blank on the last bit.

 All the 3.x ROMS I`ve seen have the same series of 16bit words at the end.
 0018,0019,001A,001B,001C,001D,001E,001F.

I just found it strange, since unused space is normally set to $FF..

[Doobrey]

I don`t think they could be vectors, as some of them would result in the code starting at odd locations. (odd as in not even, not odd as in wierd !)

 I`m beginning to think they`re just leftovers from debugging.

[Doobrey]

Ta for the info Piru,
 I`d only just stopped playing around with hacking the ROM, zeroing that pattern made no difference to anything, so like you say, just junk..
 Oh well, back to messing around again..
I just made myself a new ROM image with Piru`s Exec44.1, removed carddisk.device,workbench and icon librarys, added some BlizKick modules and replaced bits with some of the OS3.9 modules.
 Now I`ve got 80Kb free space to play with.. :evilgrin:

[Doobrey]

Don`t worry Sparky, when I`m done it`ll be a simple point and click program that`ll do it for you.
 I suppose I`d better figure out what stuff you can add to what machine, and what stuff you can`t remove too !

 There`s even more stuff in the pipeline, but if I told you, I`d have to kill you  :quickdraw:

[Doobrey]

Castellen wrote:
Check the Motorola 68000 datasheet to see if it does anything with the data at those addresses.
Could be something like reset vectors or interrupt vectors??

Bingo !
The CPU uses that data at the end of the ROM to map the hardware interrupt level to an autovector.
 Just stumbled upon this from the RKM Libs/Interrupts.. hey, it only took me 3 years to get back to this and follow Anthony's advice ! :lol:

The priority level of the new interrupt is used to index into the top seven words of the processor address space. The odd byte (a vector number) of the indexed word is fetched and then shifted left by two to create an offset into the processor's auto-vector interrupt table.The vector offsets used are in the range of $064 to $07C.