Changes

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 (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). It might be installed in US models, there isn't too much known about whether CPCs were exported to USA.... One source says that the CPC6128 was initially sold ''only'' in USA... Another source says that Indescomp (spanish distributor) produced CPCs with ''Indescomp International U.S.A.'' stickers. The 60Hz setting may cause compatibility problems with various non-BIOS software. And, due to a BIOS glitch, even with BIOS-based software (see [[Media:S968ap13.pdf|SOFT 968 Appendix 13 (XIII) (Hints Tips and Workarounds)]] for details).

The CPC6128 contains 128K RAM, RAM banking is controlled by a PAL (which assists its [[Gate Array]]). However, the 6128 mainboard can be also used for 64K computers - in that case, only 64K would be installed, the PAL would be missing, and LK5,LK6,LK8 would be installed (bypassing the RAM banking logic, and passing /CAS,A14,A15 signals directly to unbanked RAM). The CPC+ has a similar feature (see R128 below).

== CPC6128:LK7 aka CPC664:LK201 - Autoboot CP/M ==

Same as DDI-1:LK1 (see there). By default, the two soldering points are connected with each other (by a printed wire on the PCB, to activate autoboot one must scratch off that connection).In the CPC664, LK201 is located close to the power-supply connectors.In the CPC6128, LK7 is located close to the gate array.

Same as DDI-1:LK1 (see there).'''Bug:''' There's a bug in the System Cartridge, which always attempts to execute the Burnin' Rubber bootmenu at address 7:C072h, this is done even if bank 0 and 7 are exchanged, causing the CPC to crash when LK105 is changed. Workaround would be to replace opcode LD C,07h (at 05EBh in system cart) by LD C,83h (this fixes the bug), or to replace opcode LD HL,C072h (at 05E8h in system cart) by LD HL,0000h (completely disables the bootmenu, which was a rather idea annoying anyways). The same bug occurs when [[Connecting a Disc Interface to CPC464+]]. == CPC Plus:LK106 - Unknown == Purpose unknown...? Usually LK106 is not installed. (related to Upper ROM Bank signals /IORQ, A13, /WAIT, /RESET)

* The ASIC (where R129 connects to) should hava have nothing to do with the FDC. However, it does control the AMSDOS ROM bank selection: translating ROM bank 7 (or 0) to cartridge bank 3. However, bank 7 is used by the Burnin' Rubber boot-menu, so bank 7 must exist regardless of R129.* Possibly, The ASIC does output some FDC related signals /MOTOR and /FDC. Maybe removing R129 might disable disables these, though that feature (so cartridge bank 3 could would be only accessed as ROM bank 83h, but of not as ROM bank 7too much use (unless one wants to disable an internal FDC, nor 0in order to use an external FDC instead of it).

When installed (default), enables the 8th printer bit, controlled via [[CRTC]]Register 0Ch, Bit 3. When removed, outputs LOW as 8th bit (as on classic CPCs with 7bit printer port). See also: [[8bit Printer Ports]].

VCC ---LK1--- EPROM.A18---LK2---CPC.A18CA18 VCC ---LK3--- EPROM.A17---LK4---CPC.A17CA17 VCC ---LK5--- EPROM.A15---LK6---CPC.A15CA15