I bought an Amiga 1000 second-hand many years ago for $50. In this deal I received a spare motherboard as the one installed in the chassis was upgraded; most notably, it had KickStart on ROM and thus didn't require a disk at power-on (other than the Workbench, naturally).

It has been a while since I've looked at this machine, but before I go digging it out and disassembling it to see, I'm curious about this ROM modification. I know about the Phoenix motherboard, but I don't think that is what I have hiding in my basement shelves. Was a ROM-based A1000 motherboard a factory or aftermarket modification? Was this common or do I have some unusual specimen?

Last I turned on the machine (probably 2 years ago), it did work but the floppy drive needs some maintenance so I put it away for a future date. As far as opening it up to see what is inside, I haven't done that for probably 20 years.

up vote 5 down vote accepted

Here are some options for booting an Amiga 1000 without a physical Kickstart floppy disk:

Kickstart eliminators:

Accelerators with ROM sockets or flash memory:

  • CMI PAMC-1000
  • Some users report success with the Individual Computers ACA500plus on an Amiga 1000. (Remember to install it backwards! (The CF slots should face the rear of the machine.))

Replacement motherboards with ROM sockets:

Floppy emulators (boot Kickstart from SD card or USB):

  • HxC
  • Gotek
  • 1
    I can confirm that the Vampire 500 V2+ board also works in an A1000 and boots straight into its built-in Kickstart 3.1. – pndc Jan 25 at 10:09

TL;DR You will need to open up the machine to see exactly what kind of Kickstart ROM upgrade is installed.

As you are probably aware, the disk-based Kickstart boot floppy was not part of the original Amiga A1000 design. Rather, it was a last minute response to the OS still being un-polished and buggy as Commodore management rushed the machine to market. Because of this, the A1000 motherboard actually has blanks to accommodate Kickstart ROM's, and this functionality is superseded with the addition of the simplified boot ROMs and Kickstart RAM daughterboard, which together load Kickstart in the Writable Control Store (WCS).

Given that background, it is unsurprising that once the OS became pretty stable with Release 1.2, there were kits available for the A1000 that would undo the WCS "hack". Basically, the Kickstart WCS RAM would be reclaimed as usable system RAM, and the simplified boot ROMS would be replaced with actually Kickstart ROMs. This was a relatively complicated change typically involving desoldering some chips for replacement and adding additional ROM chips. One example early product like this was the Kickstart Eliminator.

Due to the difficulty of the above upgrade, the other early approach was a plug-in card for the Amiga's side expansion connector that provided Kickstart in ROM. Indeed, this is still a popular way to get an A1000 booting without floppies, and is replicated in more modern hardware in the ACA500, which works with the A1000 when flipped over.†

† Common usage is to flip the ACA500 over, not the CPU :)

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