From: http://www.amiga-news.de/de/forum/thread.php?id=26519&BoardID=1

Also see: http://www.titan.co.nz/amigaak/AA020880.htm

From the A1- XE manual:

I've read 3x correction, but of course typos are possible.

JP2: Normal, GC mode select (2-3)
GC Mode 1-2
Normal fashion 2-3

JP11, JP12, JP13: Set the system clock configuration.

    code:

      JP11 JP12 JP13 host (MHz) AGP (MHz) PCI (MHz) USB (MHz) REF. (MHz)
     2-3 2-3 2-3 Hi-z Hi-z Hi-z Hi-z Hi-z
     2-3 2-1 2-3 100 66.67 33.33 Hi-z 14.318
     2-1 2-1 2-3 100 66.67 33.33 48 14.318
     2-3 2-1 2-1 133 66.67 33.33 Off 14.318
     2-1 2-1 2-1 133 66.67 33.33 48 14.318 
J17, JP17: Core voltage switch
code:
      1 2 3 4 JP17 Vcc_Core
     on  off on  short short 1.59 7451 (G4)
     off on  off off   short 1.44 750FX (G3) (http://www.titan.co.nz/amigaak/AA020880.htm)

     1 2 3 4 JP17 VCC_CORE (V)
     Off On Off Off Open 2.24
     On On Off Off Open 2.34
     Off Off On Off Open 2.44
     On Off On Off Open 2.54
     Off On Off On Open 2.64
     On On On Off Open 2.74
     Off Off Off On Open 2.84
     On Off Off On Open 2.94
     Off On Off On Open 3.04
     On On Off On Open 3.14
     Off Off On On Open 3.24
     On Off On On Open 3.34
     Off On On Open 3.44
     On On On Open 3.54
II. CS-5155 Power Range for Articia S Switch Setting
     1 2 3 4 JP17 VCC_CORE (V)
     Off Off Off Off Short 1.34
     On Off Off Off Short 1.39
     Off On Off Off Short 1.44
     On On Off Off Short 1.49
     Off Off On Off Short 1.54
     On Off On Off Short 1.59
     Off On On Off Short 1.64
     On On On Off Short 1.69
     Off Off Off On Short 1.74
     On Off Off On Short 1.79
     Off On Off On Short 1.84
     On On Off On Short 1.89
     Off Off On On Short 1.94
     On Off On On Short 1.99
     Off On On On Short 2.04
     On On On On 2.09
     Off Off Off Off Open 1.244
     On Off Off Off Open 2.14 
J3, J4: SDRAM DIMM slots
J5: Universal AGP slot
J6: USB / RJ45 connector

J7: Infrared Connector
J8, J9, J10: Universal PCI slots
J11: Universal PCI Slot on PCI Bus 1
J14: PS / 2 Key Board / Mouse connector
J15: Parallel and serial port connector

J9A1: Header for USB 3 and 4
J16: ATX power connector

JK1: Audio and game port
J13: ROM socket

JP19: Interrupt mode select (2-3)
2-3 PowerPC / MIPS
1-2x86

JP20: CPU mode select (2-3)
2-3 PowerPC / MIPS
1-2x86

JP1: Power-on switch
JP3: IDE Hard Disk LED
JP4, JP5: Primary and Secondary IDE connectors
JP6: Floppy connector

JP31: SPDIF Out
JP32: Headphone Out
JP33: Aux In
JP34: CD In

JP14, JP15: CPU cooling fan connectors
JP16: Internal speaker connector
JP18: Reset
JP7, JP30: Reserved