A500 rev 6A - JP2 and JP7A

Summary

The A500 rev 6A has two jumpers to be able to manage how expansion memory is used.

• JP2

• JP7A

JP2

JP2 controls where expansion ram maps to - either CHIP or SLOW ram:

Connect jumper pin 2 to:

• Pin 1 = A23 -> C00000 (default) = SLOW ram

• Pin 3 = A19 -> 080000 = CHIP ram

JP7A

JP7A allows you to enable or disable expansion ram.

Pin 1 - Pin 32 on Expansion Connector

Pin 2 = _EXTICK

Pin 3 = GND

By default, pins 2 and 1 are connected together, so _EXTICK is passed on to pin 32 of the expansion connector, which will allow the expansion ram board to be enabled or disabled. Some expansion ram boards will just connect this to ground. Some expansion boards will provide an on board switch to enable to disable of the expansion ram.

If _EXTICK is floating then that indicates there is no expansion ram present.

If _EXTICK is connected to ground then expansion ram is enabled and expected. If there is no expansion ram connected then the Amiga will not boot up.