It wasn’t mentioned. I think they are referring to how the Jonathan’s bus is more similar to S-100 than a PC’s motherboard card bus. There was not a primary mother board that ran the bus like in Apple 2 or IBM PC

I ran TSR-80 systems and I never had a S-100, I was always fascinated how it could have multiple motherboards on it with different CPUs. I think S-100 was more similar to SCSI or Ethernet than to a PCI bus.

IIRC, it's entirely possible to build an Apple II on an Apple II card and let it drive a completely passive backplane with slots 0 through 7. I think it'd even be possible to drive the bus from any slot.

The Jonathan bus would probably be a lot more robust, however, as power delivery was an issue on loaded Apple II's (with too much current flowing through too few VCC and GND pins).

not really like scsi - that's more like usb with a central controller. more like VME - a bus that looked alot like a 68k bus, but supported multiple masters with a protocol to negotiate temporary ownership to assert a transaction.

there was a single address space. so every board had a set of dip switches to give it its address. which was always a big source of pain

I can't imagine apple shipping a computer product like that, so maybe you get the high bits based on what slot you're in and a config eprom to do discovery?

Interesting.

I suspect if Apple had done this they would have had someway for the cards to auto-negotiate.

A few years after the Jonathan prototype, I remember fighting with the DIP switches on PC ISA cards and setting the the correct IRQs, and then seeing a friend drop in a NUBUS card into their Macintosh II and the hardware was magically configured. I wonder if NUBUS could have multiple masters?

Apple II cards knew which slot they were in and could have small ROMs with simple IO functions.

I could see them using something like they did with NuBus — something similar to the declaration ROMs could make this sort of configuration work nicely, as long as part makers played according to the specs.