I'm not talking about X.org or KDE, I'm not using them, just the cli.
As far as I know the framebuffer (which is used for higher resolution
TEXT modes) doesn't support that resolution, so only if you're using a
proprietary video kernel module (like nVidia, AMD) the adaptor _may_
Use the "vga-ask" parameter to the kernel at boot-up to see which
resolutions _are_ supported.
BTW: it is the graphics adaptor that has to support it, it should ask
the monitor what resolutions it can support and then tries the nearest
For instance, on my nVidia Quadro FX, I'm using the full resolution
(of 1920x1200) in X, but can use only 1600x1200 in text mode.
The X resolution is done through the binary NVidia kernel (nvidia.ko)
and nvidiadrv.so X modules.