[[Category:CPC Internal Components]]
'''Links''' - Amstrad has used a number of LKs (Links) on CPC mainboards and on peripherals like DDI-1 and CPC+ Cartridges. The LKs are simply a piece of wire that is (or is not) installed between two soldering points.
== LK1,LK2,LK3 - Manufacturer ID ==
LK1,LK2,LK3 connect to [[8255|PPI]] Port B, Bit1-3. The links select the manufacturer name (which is displayed by the BIOS in the power-up message). These LKs exist on all CPC mainboards (in CPC Plus/GX4000 /Costdown schematics they are named LK101,LK102,LK103). By default, LK1-LK3 are not installed ([[Amstrad]]). Other combinations are LK2 installed in german [[Schneider]] models, and LK1+LK2 in australian [[Awa]] models. For more info see [[LK-selectable Brand Names]].
== LK4 - Screen Refresh Rate ==
LK4 (LK104 on Plus/GX4000/Costdown) connects to [[8255|PPI]] Port B, Bit4. The link tells the BIOS whether it should set-up the [[CRTC]] for 50Hz or 60Hz refresh rate.
Default is LK4 not installed (50Hz).
* 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)