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Using the Simple DirectMedia Layer on Atari

  • If you want to build SDL from sources to create SDL programs on Atari: see sections I - II.
  • If you want to create SDL programs on Atari using SDL binary build [TODO]
  • If you want to configure a program using SDL on Atari, see sections IV - VI.

I. Building the Simple DirectMedia Layer libraries:

note: This step isn't necessary if you have the SDL binary distribution

Do the classic configure, with --disable-shared --enable-static and:

Tos version (should run everywhere): --disable-threads Tos does not support threads.

MiNT version (maybe Magic, only for multitasking OS): --disable-pthreads --enable-pth

Mint and Magic may supports threads, so audio can be used with current devices, like Sun audio, or disk-writing support. Like Tos, interrupt audio without threads is more suited for Atari machines. Then you can make ; make install it.

II. Building the Simple DirectMedia Layer test programs:

Do the classic configure, then make.

Run them !

III. Enjoy! :)

If you have a project you'd like me to know about, or want to ask questions, go ahead and join the SDL developer's mailing list by sending e-mail to:

and put "subscribe" into the subject of the message. Or alternatively you can use the web interface:

IV. What is supported:

  • Keyboard (GEMDOS, BIOS, GEM, Ikbd)
  • Mouse (XBIOS, GEM, Ikbd, /dev/mouse (non working atm, disabled))
  • Video (XBIOS (Fullscreen), GEM (Windowed and Fullscreen))
  • Timer (VBL vector, GNU pth library)
  • Joysticks and joypads (Ikbd, Hardware)
  • Audio (Hardware, XBIOS, GSXB, MCSN, STFA, /dev/audio if threads enabled)
  • Threads (Multitasking OS only via GNU pth library)
  • Shared object loader (using LDG library from
  • Audio CD (MetaDOS)
  • OpenGL (using Mesa offscreen rendering driver)

- Dependent driver combinations:


- Audio driver availability

Audio driverOperating systemNotes
dma8AllUses MFP Timer A interrupt
xbiosTOSUses MFP Timer A interrupt
xbiosMiNTUses MFP Timer A interrupt
stfaAllUses MFP interrupt
mcsnTOSUses MFP Timer A interrupt
mcsnMiNTUses MiNT thread
gsxbAllUses GSXB callback


  1. Joypad driver always uses hardware access.
  2. OpenGL driver always uses OSMesa.
  3. GEM does not report relative mouse motion, so xbios mouse driver is used to report this type event. A preliminary driver for /dev/mouse device driver is present, but is disabled till it can be used with other applications simultaneously.
  4. If you build SDL with threads using the GNU pth library, timers are supported via the pth library.

V. Environment variables:

Variable namedescription
SDL_VIDEODRIVERSet to 'xbios' to force xbios video driver
Set to 'gem' to force gem video driver
SDL_VIDEO_GL_DRIVERSet to filename to load as OpenGL library, if you use SDL_GL_LoadLibrary()
SDL_AUDIODRIVERSet to 'mint_gsxb' to force Atari GSXB audio driver
Set to 'mint_mcsn' to force Atari MCSN audio driver
Set to 'mint_stfa' to force Atari STFA audio driver
Set to 'mint_xbios' to force Atari Xbios audio driver
Set to 'mint_dma8' to force Atari 8 bits DMA audio driver
Set to 'audio' to force Sun /dev/audio audio driver
Set to 'disk' to force disk-writing audio driver
SDL_ATARI_EVENTSDRIVERSet to 'ikbd' to force IKBD 6301 keyboard driver
Set to 'gemdos' to force gemdos keyboard driver
Set to 'bios' to force bios keyboard driver
SDL_JOYSTICK_ATARIUse any of these strings in the environment variable to enable or disable a joystick:
'ikbd-joy1-[on|off]' for IKBD joystick on port 1 (hardware access)
'xbios-joy1-[on|off]' for IKBD joystick on port 1 (xbios access)
'porta-pad-[on|off]' for joypad and/or teamtap on port A
'porta-joy0-[on|off]' for joystick 0 on port A
'porta-joy1-[on|off]' for joystick 1 on port A
'porta-lp-[on|off]' for lightpen on port A
'porta-anpad-[on|off]' for analog paddle on port A
'portb-pad-[on|off]' for joypad and/or teamtap on port B
'portb-joy0-[on|off]' for joystick 0 on port B
'portb-joy1-[on|off]' for joystick 1 on port B
'portb-anpad-[on|off]' for analog paddle on port B

Default joystick configuration is:
'ikbd-joy1-on' (if IKBD events driver enabled)
'xbios-joy1-on' (if gemdos/bios/gem events driver enabled)
'porta-pad-on portb-pad-on' (if available on the machine) The second joystick port on IKBD is used by the mouse, so not usable.
Another problem with the IKBD: mouse buttons and joystick fire buttons are wired together at the hardware level, it means:

port 0port 0port 1
mouse left button= joystick fire 0 = joystick fire 1
mouse right button= joystick fire 1 = joystick fire 0

Descriptions of joysticks/joypads:

  • Joypads: 1 hat, 17 buttons (Atari Jaguar console-like).
  • Joysticks: 1 hat, 1 button.
  • Lightpen, analog paddles: 2 axis, 2 buttons. The 2 buttons are those affected to 1 button joysticks on the same port.

VI. More informations about drivers:

Driver nameDescription
OpenGLThe default is to use the Mesa offscreen driver (osmesa.ldg). If you want to use an older OpenGL implementation, like mesa_gl.ldg or tiny_gl.ldg, your program must use SDL_GL_LoadLibrary() to do so, and retrieve the needed function pointers with SDL_LoadFunction(). In all cases, the OpenGL context is taken care of by SDL itself, you just have to use gl* functions.
However, there is one OpenGL call that has a different prototype in the old implementations: glOrtho(). In the old implementations, it has 6 float as parameters, in the standard one, it has 6 double parameters. If you want to compile testdyngl, or any other SDL program that loads its OpenGL library, you must change the glOrtho() prototype used in this program. In osmesa.ldg, you can retrieve a glOrtho() with double parameters, by searching for the function "glOrtho6d".
Xbios videoVideo chip is detected using the _VDO cookie. Screen enhancers are not supported, but could be if you know how to use them. CTPCI/ATI Radeon is supported.
ST, STE, Mega ST, Mega STE: 320x200x4 bits, shades of grey, available only for the purpose of testing SDL.
TT: 320x480x8 and 320x240x8 (software double-lined mode).
Falcon: All modes supported by the current monitor (RGB or VGA). BlowUp and Centscreen extended modes, ScreenBlaster 3 current mode, CTPCI/ATI Radeon common video modes.
Clones and any machine with monochrome monitor:
Not supported.
Gem videoAutomatically used if xbios not available.
All machines:
Only the current resolution, if 8 bits or higher depth.
IKBD keyboard, mouse and joystick driverAvailable if _MCH cookie is ST, Mega ST, STE, Mega STE, TT or Falcon.
Hades has an IKBD, but xbios is not available for video, so IKBD driver is disabled.
Gemdos and bios keyboard driverAvailable on all machines.
Mouse and joystick xbios driverAvailable on all machines (I think).
Joypad driverAvailable if _MCH cookie is STE or Falcon. Supports teamtap.
PTH timer driverAvailable with multitasking OS (FreeMiNT).
VBL timer driverAvailable on all machines.
Audio driversCookies _SND, MCSN, STFA and GSXB are used to detect supported audio capabilities.
STE, Mega STE, TT 8 bits DMA (hardware access), STFA, MCSN or GSXB driver if installed
Atari Falcon 8 bits DMA (hardware access), Xbios functions, STFA, MCSN or GSXB driver if installed
Other machines STFA, MCSN or GSXB driver if installed.