I was testing some slab motherboards yesterday and I needed to get into the ROM monitor.
I did a quick experiment and found that colour slabs (turbo or not) would boot with an ADB soundboard, but the keyboard and mouse are not seen until after the ADB bus is initialized (fairly late in the game). OTOH. If I used a non-ADB soundboard with non-ADB keyboard+mouse, the keyboard is recognized immediately, and the OS handles the non-ADB devices just fine. So, I have a few questions about ADB peripherals:
1) Which ROM versions support ADB devices?
2) How does one break into the ROM monitor with ADB devices? The ALT+COMMAND+~ sequence didn't seem to work.
3) Is it possible to change the ROM in a mono slab to have it work with ADB peripherals plugged into a soundboard?
Given what I saw, I thought it somewhat peculiar that Apple hadn't put the ADB host controller in the soundboard, and simply converted ADB keyboard+mouse into non-ADB protocol. Would people be interested in such a protocol converter (I'm already doing a PS2 to non-ADB protocol converter... so adding support for USB/ADB later seems reasonable). If the answer to (3) is 'no' then this would provide a way to connect ADB keyboard+mouse to older machines (though I prefer the older devices myself...).
afak, only rom rev .74 supports adb during boot.