single head is using only one display head while dual head is using two.
One of the limitations with the current ATI fglrx drivers is that it does not allow three display heads -- so no dual LCDs and a TV-out running concurrently. ATI's Big Desktop works quite nicely for two monitors.
With aticonfig look after the Dynamic Display Management Options, and there are some related options in the --help.
Big Desktop uses one X server where as the true dual head mode will use two.
I am afraid I may be misinterpreting your question. You can work on two desktops if setting up Big Desktop or dual head modes. Those can be done through aticonfig using aticonfig --initial=dual-head or aticonfig --dtop=horizontal
Looks nice, I will try it out next time I turn on a KDE box. Are you going to implement any PowerPlay functions with the program?
Yes, but it will take some time for me. I will have to learn to play with Array functions of Kommander, since the options have to be read from the aticonfig -lsp output.
Does GTK have anything like Kommander? I will not do it, but it must be pretty simple to transfer what I have done to another tool like that.
Regarding the double head: I once tried it, so it really seemed like two x sessions were started, and I saw a completely new (and empty) desktop on my TV head. However, I could not figure out how to do things on both desktops simultaneously.
E.g., could I edit a document on one desktop while playing a movie on another via tv-out? How do I switch to work from one head to the other?