i'm suprised that your cpu is blocking at 600MHz, it is the low frequency of speedstep :/
if i well understood about EIST, it's managed by 2 parts:
1- the bios: Don't you have a speedstep or EIST setting in your bios ?
2- the OS, via power managing ... and soft ?
For my part, under my Asus, i have Power4Gear which offer a list of profiles to manage the CPU, screen, ...
The "lowest" profil, a "Battery Saving" let the CPU at the lowest, everytime.
The "High performance" & "Super Performance" let the CPU at its max frequency/voltage
"Game", "DVD Movie" (battery mode) and others scale frequence/power.
I don't know if without this soft XP uses the speedstep and scale the frequency too.
If you can't see the setting of SpeedStep in yout bios, CpuZ should tell you, and intel cpu identifer too.
Personaly, i have a problem with SpeedStep, but under Seven, and i use CrystalCpuId (which can set Coeff / VID, and have a managing mode with 3 levels for scale mi/avg/max) on waiting for a proper driver (intel ? MS ? )