Bienvenue sur les forums bodhi.Profitez de votre séjour!Grâce à Google Traduction =)
I also installed 4.1 recently, and although a part of it is Ubuntu, a lot of it isn't. Have fun! It sure feels different to open/power on a laptop that boots directly to Bodhi! I will provide a screenshot soon
Back then when I attempted an xrandr with a1440x900 resolution or even a 1600xsomething on my graphics hardware, I had to have that modeline in my xorg.conf first. That way, xrandr could then display it properly, since it was already listed or defined. The log file was very handy in providing me with the other possible resolutions. I knew there were about a dozen others since I would go into "video modes" while setting up a first person shooter for optimum framerates.
Use the log file while tweaking xorg.conf when setting up mutiple display monitors, especially when each display supports different resolutions.
I would create an xorg.conf that defines that mode, and many others. This is a solution that works for all cards regardless of era, but it is quite lengthy and the subject of ancient HOWTOs that can be glommed off the net. This was before Ubuntu was created, and when xorg was more than the autodetected configuration file. Many people would copy and paste, and make it work. birdmun is pointing the way, and if you need to learn more, there are examples of xrandr on thinkwiki, the wiki for Thinkpad users. Your google-fu will get quite the workout here. If it worked on Puppy, boot the Puppy stick or USB, find out how it worked, then mimic that on Bodhi. (1280x800 is working fine here on my DELL Latitude 6440, currently running BL 4.1.0, but then mine has onboard Intel and not dedicated graphics card)
What is the resolution when the grub screen is shown, if you can set it higher, then that's a good start. There is a thread here in the forum to set it better or higher than 640x480, so that plymouth can run or diagnostic boot message text can display properly.