Same as DDI-1:LK1 (see there).
== GX4000:LKs ==
* LK1-LK4 - same as CPC, though being not actually used by (absent) BIOS
* LK5 - none such...?
* LK6 - purpose unknown...? (related to /IORQ, A13, /WAIT, /RESET)
* LK7 - shortcut +5V with +5VMOD (use same supply for computer and modulator)
== CPC Plus:LK105 - Autoboot CP/M ==
Same as DDI-1:LK1 (see there).
== CPC Plus:LK106 - Unknown ==
Purpose unknown...? (related to /IORQ, A13, /WAIT, /RESET)
== CPC Plus:R128 aka R28 (10kOhm) - 128K RAM Enable ==
VCC ---LK5--- EPROM.A15 ---LK6--- CA15
Some cartridge PCBs don't have any LKs installed, instead, the etched circuit has hardwired connections between some of them. One could scratch them off, and then use the LK soldering points to reconfigure the board for eproms of other size.
== GX4000:LKs ==
* LK1-LK4 - same as CPC, though not being actually used, due to absent BIOS
* LK5 - none such...?
* LK6 - same as LK106 on CPC+
* LK7 - shortcut +5V with +5VMOD (use same supply for computer and modulator)