I have ATI Radeon X1250-based graphics onboard (on my ASUS M2A-VM MotherBoard),
working fine... but every time i start my X Server (with gdm)
i can see a screenshot of the last session (just for a moment).

how can that be?

i checked this after:
1. having booted a windows,
2. shut down it
3. powered off my computer
4. started up my debian
then i saw the windows login screen before the (graphical) login manager has started.

when the last booted OS was my debian its just a screenshot of my debian login screen.

so my questions are:
1. why is my graphic card able to save that screenshot?
2. where does my x server (or my gdm???) take those screenshots from?

Could it be that somehow that data stays on the video card RAM even after shutdown. Does this happen if you turn off the computer and let is sit overnight, then boot it up in the morning or only after immediately or shortly afterward booting it up again (restarting) ?

Do you see the post messages for boot up and then just before the graphical login the flash of the previous login?

i can see this pictures even if the computer was powered off the whole night (plugged off power connector).

sniff: its just the moment when the x server starts up. before i can see normal boot messages.

Maybe some memory being flushed when the graphics driver kicks in. Its a strange one though, I have never seen anything like that.

The integrated graphics card in question has little memory... it uses hypermemory up to 1 GB (basically a faster PCIE way of using part of the onboard RAM). How much are you using? (Check BIOS).

will check that.

Doesn't it always use the same memory addresses? In which case it could be something sitting in the addresses thats gets flushed...?