Increasing the number of ISA slots

[spaceman88]

The Tower expansion units do just that, add more ISA slots for either a BridgeBoard or Toaster.

The IBM expansion model would likely work, but why?

Yes, my Ambitious Technology 4000 tower has an Amiga 4000 desktop motherboard and a big board ( I think it was called "Big Bertha") full of ISA slots for TBC's etc.

BTW, having the motherboard mounted on it's side saved it from the dreaded NiCad. The battery had leaked, but the liquid dripped off the board on to the bare metal at the bottom of the case.

[spaceman88]

Not the NiCD battery solution everyone is looking for, but A+ on the effort

I removed the battery as soon as I got the unit from the previous owner, but there is one more 4000 motherboard still working because it was in a tower.

[spaceman88]

I believe the TBCs only used the ISA bus for power though.  I bet all the other lines weren't connected for some of those towers.

edit:

yep...    http://www.bigbookofamigahardware.com/bboah/product.aspx?id=1837

Yes, the TBC in my tower was controlled by a cable from the serial port to what looks like a phone jack on the TBC. The video in/out is on the external jacks going to the Toaster, so the ISA slots just hold them in place and feed them power. I see from your link my expansion board was called "Big Ethyl" (not bertha, as I said before).