XFBdev resolution platinum 7200/90

[cesagbo@b2b2c.ca]

Hi, 
        I`m using a 7200/90 with a platinum video adaptor 1mb.  
        Debian woody is used with a 2.2.20-pmac kernel and 4.x.x Xserver
        The platinum framebuffer work very fine in 800x600.
        
        I haven`t been able to use a resolution of 800x600 with X. The xf86config-4 as been properly configured but the server fall back to the original platinum framebuffer résolution 640x480 16 bits. A line say "can`t use mode vt7" before the Xserver goes on in 640x480.  
        
        I`ve tried to change the résolution while booting but it seem i don`t know how to do it.
        at bootX ---> video=platinum:vmode:800x600-60
        
        The XFBdev doc. are not very spécific about the platinum.
        The kernel doc. is very general too.

    Can i use a pc ati mach64 in a powermac?  I gess not, because of the pci bus speed diff. (33/45Mhz) and the bios of the card...
               
                                                       Charles   :^\