How do I get more than SXGA mode in KDE3.4?

[tomohiko kitamura]

hello,

How do I get more than XGA(SXGA) graphics mode in KDE desktop?

linux OS:SLACKWARE10.1
kernel  :2.4.29 (with make commands)
video   :fireGL(radeon)8700(driver was installed manualy)
CPU     :PIII-800
RAM     :512MB
HDD     :6GB
lilo boot at SXGA(1280-1024)mode,
but startx / KDE desktop is XGA(1024-768)graphics mode.

CRT(VESA/DCC MAX2048-1536)

tomohiko kitamura