Here are the specs. Think it would run HL2?
NAME 600 / 800 XL
MANUFACTURER Atari
TYPE Home Computer
ORIGIN U.S.A.
YEAR 1982
END OF PRODUCTION January 85
BUILT IN LANGUAGE Atari Basic
KEYBOARD Mechanical keyboard
CPU MOS 6502C
SPEED 1.79 (NTSC) / 1.77 (PAL) MHz
COPROCESSOR GTIA (video), POKEY (sound, I/O), ANTIC (video)
RAM 16 KB (600 XL up to 48 KB) / 64 KB (800 XL, expandable to 128 KB)
ROM 24 KB
TEXT MODES five text modes, max: 40 x 24, min: 20 x 12
GRAPHIC MODES 16 graphic modes, maximum : 320 x 192
COLORS 256 (16 colors with 16 intensities)
SOUND 4 voices, 3.5 octaves
I/O PORTS Composite video output, cartridge slot, peripheral port (SIO), parallel bus, 2 joystick plugs
POWER SUPPLY External power supply unit