A series of computer cards using the VME bus as a common backplane, in the style of laboratory test equipment and modular industrial computers.

I've always liked the VME bus for its adaptability. It's an asynchronous bus with dynamic sizing, so it can support both controllers and peripherals that require different signaling speeds and bus widths to communicate, without requiring a specialized bus interface chip. It supports multiple controllers without the need for a special slot on the backplane, because it uses daisy chained priority bus arbitration. It uses standard and readily available DIN41612 connectors, comes in a 3U variant, and it's possible to still buy equipment that conforms to the standard, namely card cases and power supplies. The 3U Eurocard standard, which uses 160x100mm boards, is also fairly affordable for PCB printing, and it's possible to make 100x100mm cards, which can be printed for as low as $2. The bus is perhaps slow by modern standards, but for CPUs that are below 100MHz, it's the perfect bus to build 16-bit and 32-bit retro computers around.

My intention is to build a backplane, dedicated bus arbitration and interrupt controller card, and a generic 68030-based CPU card to start. I'll buy an off-the-shelf card case (possibly from Schroff) and adapt a cheap power supply. I'm hoping to be able to install multiple CPU cards into the same system to make a simple multiprocessor machine. I'll also make either a Fidget-based FPGA card, or a microcontroller-based card for debugging the bus, and acting as the first peripheral card on the bus.

Once the base system is complete, I'll make a RAM board, possibly a disk drive or CompactFlash controller card, and an ethernet card. I also intend to eventually make a 68010 version using only DIP chips and hopefully all hardwired logic, so that a specialized PLD programmer won't be needed to build one. I might also make cards with other CPUs. It should be possible for the system to support different CPUs in the same system at the same time. My larger hope is for the VME bus to be used more broadly in the hobbyist computer community as a common means of interoperability.

• it uses the eurocard form factor, and equipment such as cases can still be bought new or used

• it's asynchronous, so it can support devices operating at different speeds

• the DIN41612 connectors it uses are still widely available with solder tails

VMEbus prototyping card PCB: https://github.com/rhaamo/VME

Proto Boards, Blanking Plates, Plate Adapters, ECB backplanes: https://www.ebay.ca/usr/martenelectric

COMET backplane, prototyping card, and single board computer: - https://hackaday.io/project/192539-comet68k - https://github.com/tomstorey/COMET - computer card is missing bus arbitration, but the backplane supports it