From my experience an A3000 w/o daughterboard yields a yellow screen on bootup (i.e. won't boot). But you can boot an A4000 even w/o the daughtercard installed. Has to do with the way the bus autoconfig differs on the A4000. The daughtercards are not interchangeable and notice that you can't use the same 3rd party replacement daughterboards (including pci ones) for the A3000 and A4000 desktop models.
You should check all the jumpers on the mainboard for the proper configuration for the A3640, which differs from the A3630 board setup in having its own clock. The Rev.3 A3640s have a couple of hardware problems (i.e. you may not get it to work with every version of 68040.library or there may be hardware bus conflicts with your Superbuster chip, Rev.11 is best).
