OPENCBM(4)

NAME
opencbm - OpenCBM driver for parallel-port X[MA]-1541 cables

SYNOPSIS
opencbm

DESCRIPTION
The opencbm driver supports Commodore disk drives connected to the parallel port using an XM(P)-1541 or XA(P)-1541 cable.

  Loader Tunables
The following loader tunables are used to set driver configuration at the loader(8) prompt before booting the kernel, or they can be stored in /boot/loader.conf in order to automatically set them before booting the kernel. It is also possible to use kenv(1) to change these tunables before loading the opencbm driver.

cbm.cable
    Set to 0 or 1 to explicitly select an XM-1541 (0) or XA-1541 (1) type cable. The default value of -1 will attempt to auto-detect the cable type, which only works reliably when cbm.reset is active and the drive is connected and powered on while loading the opencbm driver.

cbm.hold_clk
    Set to 0 explicitly to release the CLK line of the bus when idle. The default (1) is to strictly follow C64 behavior, always holding the CLK line.

cbm.reset
    When set to 1 (default), execute a bus reset and wait for response from the drive while loading the opencbm driver. Set to 0 explicitly to load the driver without having to wait for the bus. In this case, you should also select a cable type explicity.

FILES
The opencbm driver creates the following device node:

/dev/cbm
    Device for communicating with a Commodore disk drive over a parallel-port cable.

EXAMPLES
To load the driver with a drive connected and powered on, auto-detecting the cable type:

    kldload opencbm

To load the driver without issuing a bus reset and selecting an active (XA-1541) cable:

    kenv cbm.cable=1
    kenv cbm.reset=0
    kldload opencbm

If you want to load the driver at system startup, adding it to kld_list in /etc/rc.conf, it is recommended to disable cbm.reset and explicitly select a cable type in /boot/loader.conf, e.g. add the following lines for a passive (XM-1541) cable:

    cbm.cable=0
    cbm.reset=0

SEE ALSO
The cables supported by the opencbm driver (XM-1541, XA-1541 and their variations) are described on https://sta.c64.org/xcables.html