Changes
Undo revision 61602 by TFM - AMSDOS uses CALL B912 for deciding whether to boot CPM, as far as known AMSDOS doesn't check PPI inputs, so LK5 must affect ROM banking - correct me if that's wrong!
* LK1-LK4 - same as CPC, though not being actually used, due to absent BIOS (though game cartridges could check LK4 to determine the desired video refresh rate) (default is LK1-LK4 not installed, equivalent to Video=50Hz, and Manufacturer=Amstrad)
* LK5 - none such (corresponding PPI input is floating, neither having a LOW level, nor a stable HIGH level) (This meaning the ROM Bank0=BASIC and Bank7=AMSDOS are unstable on GX4000, this seems to be the reason for the CPC+ System Cartridge not booting properly on the GX4000. If the AMSDOS senses the wrong signal, it tries to boot CP/M)
* LK6 - unknown (same as LK106 on CPC+) (usually LK6 is not installed, neither in GX4000 nor CPC+)
* LK7 - shortcut +5V with +5VMOD (installed in french version, which has no TV modulator)
