Using LS-DOS with M3SE

Note: The LS-DOS operating system is for Model 4/4D/4P systems only. It does not work with the Model III.

M3SE units sold after March 20, 2016 come with LS-DOS 6.3.1 pre-installed. Earlier systems can easily add an LS-DOS installation by following these instructions.

Before proceeding, please make sure your LDOS version of the IDEBOOT utility shows version 2.0 or greater when run without arguments. If yours is older, you can download the latest version from the archives here and install it on CF drive :0. Remember, you might have to log in using the password UTILITY or the system password RS0LT0FF to overwrite the existing file.

LS-DOS is installed by default on CF image 1 (LDOS is on CF image 0). Boot into LDOS, then test your LS-DOS configuration:


If you do not want LS-DOS to become your default operating system, you can simply use this method to boot LS-DOS from within LDOS. If you want LS-DOS to become your default operating system (sometimes or all the time) read on.

If you are using a Model 4P, you can move DIP switch 1 to "on", and LS-DOS will become your default boot DOS at poweron or after a hard reset.

If you are using a Model 4 or 4D, you will need a boot floppy to boot directly to LS-DOS. First, format a double-density, single-sided, 40-track floppy. Then, from the LS-DOS prompt (assuming the floppy is in drive :6):


to write the boot floppy. Then you can move DIP switch 1 to "on" and boot LS-DOS using the boot floppy.

Most of the M3SE LS-DOS utilities and applications work identically to their LDOS counterparts; see the corresponding web pages on this site for instructions. One exception is the VGA driver which needs a few more instructions to install or disable, so a couple of JCL scripts have been added:


to install the driver, and


to disable it. Note that the driver will remain in high or low memory, so it's generally not a good idea to issue a SYSGEN command until you've rebooted to remove the driver.

There is an additional switch, -B, for the FTPD application. This causes LS-DOS passwords to be bypassed, permitting all access to all files. Use this switch with due caution. It was added because, unlike LDOS, LS-DOS does not have a system password that works with any file.

Here's a link to an archive of the latest LS-DOS files for M3SE:

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