對了..,因為SGI 1600sw是24bit面板,
而我的ATi VE只有16與32bit的選項,想說是不是我的DVI無法輸出24Bit的關係
到ATi網站search的結果,他寫著:

NOTE: 24 and 32 bit modes produce the same number of colors - 16.7 million. They differ only in the organization of video memory (3 bytes per pixel for 24 bit, 4 bytes per pixel for 32 bit).

http://www.ati.com/support/infobase/3240.html

(而我用G400 D-SUB使用24Bit與32Bit看起來並無什麼差異)