Amiga Boot Selector (Part 1) What is it ?

What is an Amiga Boot Selector :

This interface makes it possible to use an externally connected Disk Drive (or Gotek Floppy Drive Emulator) as a boot disk.
This is made possible by making the amiga believe that the external drive is DF0: (Kickstart 2 and newer also have this as a software implementation, but that is a non-functional solution for some games)
Simply you can swap 2 address lines in the amiga so that DF0: internally is disabled , and DF1: becomes DF0: and is addressed as such.
In order not to have to solder and mess around with wires, there are ready-made solutions for that:
An Amiga Boot selector

Shop: Amiga Boot selector side view

Shop: Low Budget Amiga Boot Selector, A so called Tower of Power

The Amiga boot selectors come in a number of forms, but in fact they all do the same thing :
swap 2 address lines, one does it buffered, the other without buffers, one opts for a tower of power solution (3 IC sockets stacked with somewhere in the middle the pin exchange), the other has a beautiful printed circuit board in the most beautiful colors, there are some with a semi permanent setting, there are some with a switch, which give you the option to switch at a time.

I regularly get the question what the buffer adds to the Amiga boot selector :
- The IC (The buffer) works as an electronic switch (mechanical contacts can cause sparks)
- The signal that is diverted makes its way to the switch with an unbuffered boot selector, through the switch and back to the motherboard, with a buffered one the reroute is done within the IC.

Amiga 2000 boot selector :

For the Amiga 2000 you most likely will need a different bootselector than for the amiga 500 / 500+
This is caused by the fact that the Amiga 2000 reserves DF1: to be used internally, and automatically assigns the externally connected drive as DF2: (and if a 2nd drive is connected externally, it automatically becomes DF3:)
So if you use a regular DF0: - DF1: switch, at best it will boot from the second internal drive if connected (Gotek or HD drive)
If you have 2 normal amiga drives internally there's no use in booting from  the second drive if it is the exact same drive..
You could use a configurable DF0: - DF1: / DF0: - DF2: Bootselector , which allows you to select the 2nd internal drive or the 1st external drive by the means of a few jumpers.

DF0: - DF2: Bootselector

Risk of all Amiga boot selectors with a switch are equal :

  • Switching ONLY when the Amiga is off, yes it is possible when it is on, until that one time it couldn't... so don't do it !!
  • Amiga 500 has a cover over the motherboard, in many cases the increase of the kickstart appears to ensure that the can no longer fits properly.
    (This can be solved by removing the can completely, or by cutting a recess so that the boat selector is no longer covered.) The amiga works fine without the cover can, it's more of an aesthetic choice whether you want thatūüôā
  • The internal DF0: drive is completely disabled with all types of boot selectors.¬†(So ‚Äč‚Äčthere's no switching places)

The advantage you create by installing an Amiga  Boot Selector is that you can 100% hardware-wise convince your amiga that your external drive is DF0:, so there will be no compatibility problems if there is a program that wants to directly address the hardware . (That's where the software solution goes wrong, if games or intros directly address the hardware, instead of addressing it neatly via the kernel.

Furthermore, for a lot of people not unimportant, you don't have to (re)build anything on your amiga to place the Gotek internally, just use it externally by means of an external gotek interface.
You have the display in front of you instead of around the corner, you see what you do to operate the buttons.
Placing a Amiga Boot Selector is a minor intervention, it must be done accurately, which is an absolute necessity.

The CIA 8520 chip is becoming scarce, and therefore expensive, so it is important to keep it intact.

Installing the Amiga Boot Selector is covered in Part 2

Amiga Switchless Bootselector DF0: - DF1:

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