Okay, here's that Velvet ROM-dumping program!
Write the ADF to a disk. Leave it write-enabled.
Power on Velvet system, insert the disk. Press Ctrl-Amiga-Amiga to reset.
Initially the screen will be yellow for a couple of seconds. As ROM data is written to the disk it flashes black/white. When finished the screen goes green. If there is a write error screen will go red.
Not tested on real hardware, but seems to work in WinUAE.
Edit to add: The 512KB at $F80000 is written to disk starting at track 1 side 0 (so offset 11264 in the ADF file).
Edit 2: if you accidentally boot with the disk write-protected the screen will go red, but I forgot to turn the drive motor off in that case. You'll probably want to reset then quickly remove the disk instead of removing it with the motor spinning.
Last edited by mark_k; 04 May 2015 at 20:02.