Overclock ACA620 to 25mhz

[AmmoJammo]

I'd probably be running it at stock speed till you have a heatsink fitted

[AmmoJammo]

The ACA620 appears to have been designed with the idea that you can't overclock it unless there's a heatsink fitted over the cpu, which connects the two heatsink mounting holes together, allowing the overclocking to be enabled.

One mounting hole is simply connected to ground, so you can use any ground point for this, meaning, if you want to use the same switch to overclock the cpu, and enable the fan, make sure the ground "input" to the switch is solid, and use the output from the switch to go to the fan as you suggested, shouldn't be an issue.

[AmmoJammo]

There's 12v and 5v on the floppy connector - 12 is yellow, 5 is red.

Not in the Amigas it isn't.

If you're worried about grounding the fan through the accelerator, (which probably isn't a good idea) then just get your ground point to the switch from the floppy connector, and have the output from the switch still going to the accelerator (to the screws ground pad, just above connector "CN1")

[AmmoJammo]

The floppy and hdd in the amigas are 5 and 12volt, but those aren't the colours.

Amiga decided to be different (it was probably before the standard was in place) so if you're wiring things up make sure the voltages are correct.

[AmmoJammo]

Brown is 12v and red is 5v I dare say... :angry:

That would be incorrect, In the Amigas, its normally that Brown is 5volt, Red is 12volt.

[AmmoJammo]

Do this:
-Ground to the floppy ground wiring, to the centre contact of your switch.
-Power from the floppy power, to the fan power (either 5volt or 12volt depending what fan you choose)
-"output" from the switch to the fan ground, as well as the ground contact on the ACA620