CPC Expansion Backplane
This is a selection of expansion backplanes for the Amstrad CPC computers.
- cpc_backplane V1.00 provides 3 Mother MX4 compatible box connectors
- cpc_backplane V1.10 provides 4 Mother MX4 compatible box connectors and a pass-through connector
- cpc_backplane_edge V1.00 provides 4 Mother MX4 compatible box connectors and an edge connector (shown above)
All three board designs have been built and fully tested.
The two 4 slot cards are identical apart from the pass through connector being replaced by an reproduction of the Amstrad CPC edge connector. This is useful if you need to use any legacy edge connector peripherals as well as the newer MX4 slot types, and particularly for CPC464 users who may have a DDI-1 disk drive controller or DDI-3 USB interface.
The expansion slots on all cards are fully compatible with modern Amstrad CPC Peripherals such as Duke's M4 Card, the X-MEM RAM/ROM board and of course the RAM, ROM and Z80Tube expansions all described in the GitHub repositories here.
All cards provide the choice of providing power to the expansion slots either from the Amstrad CPC's own +5V supply (taken from the edge connector) or an external +5V regulated supply. On the 3 slot card power can be selected per slot by setting the jumpers appropriately. On the 4 slot cards, a single jumper sets the power supply source for all slots and the pass-through connector as a group. So, although the 4 slot cards provide for more expansion capabilities, in this regard the 3 slot card is a little more flexible. Individual slot power control can be useful during expansion card development and test for example, where you might need to measure power and/or vary voltage to a single card while keeping the others running at a steady 5V.
The 4 slot cards provides a pass-through connector either as an IDC box header or as an edge connector, so that multiple boards can be daisy chained together with a short IDC ribbon cable connector. The edge connector version allowed legacy CPC peripherals to be used when the backplane itself is already hogging the original CPC expansion port.
The backplane needs a ribbon cable to connect to either the edge connector of a CPC 464/664/6128 or the Centronics connector found on the 6128 and 464 plus machines.
PCBs are available from SeeedStudio via the Seeed Gallery.
Alternatively all Eagle .brd files and zipped archives of Gerbers are available in this repository's Releases Directory directory for you to have PCBs made wherever you choose. The expansion card with edge connector has its own release area.
A complete Bill of Materials (BOM) is available at DigiKey (UK):
You may of course source your parts anywhere but this is the reference BOM. Note that the DigiKey BOM includes a 50W edge connector, cable and IDC connector. If you have one of the Plus machines you will need to swap the 50W edge connector for a suitable Centronics-type connector.
All components are placed on the top side of the board. Note the positions of the polarising keys on all sockets/plugs to be compatible with MX4 cards.
All programs and data files in this project are made available under the terms of the GNU General Public License v3.