# Torch Z80 Co-Processor

BeebEm emulates the Torch-Z80 co-processor board. The Torch-Z80 board was an add-on card to the BBC computers which allowed you to run CPN (a clone of CP/M) software. It was Z80 based, came with 64K of RAM and connected to the BBC via the Tube interface.

The Torch had no hardware I/O of its own but used the display, keyboard, disc drives, etc of the host processor. Although it used the host disc drives, the disc formats were different to DFS or ADFS. It still used 80 track, double sided discs (400K) but these discs cannot be read on the BBC without special disc converting software. If you wish to create your own disc images of original Torch Z80 software you can use the XFER 5.1 program.

The emulator comes as default with Torch-Z80 support disabled (to prevent confusion for new users). To configure support, you need to load a sideways ROM image for the Host Tube support. A configuration file has already been created for this so the simplest thing to do is replace the Roms.cfg file with the Roms_Torch.cfg file (backing up Roms.cfg first of course!) This file simply loads the required MCP120-CBL (for BBC B with BBC with 8271 FDC) or MCP122-ABM ROM (for BBC Master).

With this new configuration, running the emulator will default to a blue Mode 0 screen. You need to enable the Torch Z80 Second Processor from the Hardware → Second Processor menu (the emulator will reboot) and type *MCP to enter CPN. If you try and run *MCP without enabling the Torch Z80 Second Processor off the Hardware menu, you will get a 'No Z80!' error message on screen.

By default, the system will try and autoboot from Drive C and if you don't have a suitable disc image mounted, it will bring back an error. To prevent this, when typing *MCP, hold down the `Alt` key (`Caps Lock`) and this will prevent CPN from autobooting.

I cannot give you a full overview of CPN but typing HELP is a good start as well as exploring the disc images found at Torch Discs.

The original Torch Standard Utilities Ver 2.0 disc and Hard Disc Utilities Ver 4.0 are included with BeebEm. These contain several useful programs to get you going.

The Torch Z80 fully supports Econet emulation which provides TORCHNET facilities for sharing drives amongst multiple computers or instances of BeebEm.

If you have any specific questions about the Torch-Z80 support, please drop Jon an e-mail - see Jon's Site.