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CON - Graphical Console Server Reference Manual


Con is graphical console server for DROPS. The hardware is hidden behind a ``virtual'' framebuffer abstraction and accesses from multiple clients are synchronized. We denote the implemented protocol as pSLIM (``pseudo'' [S]tateless [L]ow level [I]nterface [M]achine as proposed by SUN at SOSP 1999).

Con clients may receive input events (currently only from keyboard and mouse) by implementing the stream server interface. There are stubs available for L4Linux and XFree86 4.1.0.

Con offers limited hardware acceleration for the following graphics cards:

The console server supports also fast YUV-to-RGB conversion using MMX functions of newer x86 processors. Supported graphics cards with backend scaler (see previous list) do the YUV-to-RGB conversion in hardware.


For most purposes, starting con without any arguments should be sufficient. Possible command line arguments are:
-a | --noaccel
Disable autodetection of accelerated graphics cards and use none-accelerated mode. Try this if you encounter problems with not/wrong detected graphics cards.

-i | --l4io
Use l4io to scan the PCI bus and to map I/O memory. Use this option if you also load the l4io server.

-l | --nolog
Don't use the logserver as output but use the kernel debugger interface for direct log output. This is useful if the log server is logs to a virtual console itself.

-o | --omega0
Allocate interrupts using Omega0 server.

-p | --pan
Try to pan the graphics memory so that the status line begins at 4MB page granularity. This prevents an application from overwriting the statusline if it has mapped the graphics memory.

Con expects the Common L4 Environment (L4env). The following servers are expected at runtime:

A GRUB menu file resides in con/doc (menu.lst) and you should read con/doc/README.


As mentioned before, con supports an interface we denoted as pSLIM. See

There is a client library available allowing text output using pSLIM:

About this documentation

Additional information can be found at (in German, outdated).

Christian Helmuth, Frank Mehnert

DROPS Console User Manual, part of DROPS  © 2000-2003