求教：剛買了一電腦,cpu是AMD Sempron(TM) 3200+ (1.8GHz / 256KB L2

通過查CMOS Setup，cpu speed 確實是1.8GHz.但是在Windows中Right-click My Computer and select Properties. The processor type and speed is shown in the lower portion of the Properties window (on the General tab). cpu隻有991MHz。請問這是怎麽回事？