The machine below is an IBM PC AT (Model 5170) with a 6Mhz 80286, 640K of conventional memory, no extended memory, a Color Display, a 1.2Mb and a 1.44Mb diskette drive, and a 10Mb hard disk. It boots the BASIC-DOS Protected Mode diskette, which runs the same three consoles as the 2Mb Protected Mode demo, each on its own page of video memory. Use SHIFT-TAB to switch between them.
Protected mode can run in as little as 256K of conventional memory; any additional conventional or extended memory is just a bonus. See Supported Machines and The System Area for more details.
The diskette’s CONFIG.SYS defines three full-screen 80-column consoles, each running its own copy of COMMAND.COM: HELLO.BAT in the first, FIBO.BAT in the second, and PRIMES.BAS in the third. Each session’s memory is in its own LDT (local descriptor table), so a session’s programs can’t name another session’s memory. Only the page of the console with keyboard focus is displayed, but every console keeps running.
The boot sector first displays System starting...; press any key (or wait 2 seconds) to boot from the diskette, or press Esc to boot from the hard disk instead. Note that bypassing the diskette and booting from the hard disk will give you only one full-screen console.
REM Multiple Video Pages (0, 1, and 2) in protected mode
CPU=80286
BUFFERS=4
CON=VKD$:80,25
SHELL=C:COMMAND.COM PATH$="C:\;C:\EXT;C:\DEMOS;C:\SAMPLES;C:\TOOLS":HELLO.BAT
CON=VKD$:80,25
SHELL=C:COMMAND.COM PATH$="C:\;C:\EXT;C:\DEMOS;C:\SAMPLES;C:\TOOLS":FIBO.BAT
CON=VKD$:80,25
SHELL=C:COMMAND.COM PATH$="C:\;C:\EXT;C:\DEMOS;C:\SAMPLES;C:\TOOLS":PRIMES.BAS
Copyright (c) 2020-2026 Jeff Parsons Released under MIT License