Vmax is the maximum non-operating (failure) voltage.
Regarding the chip's wattage numbers, Intel states: "The [Thermal Design Power] numbers ... reflect Intel's recommended design point and are not indicative of the maximum power the pr, ocessor can dissipate under worst case conditions."
If, , , the on-Die thermal probe reaches approximately 125° C (its catastrophic temperature), the CPU will automatically shut down and "the system bus signal THERMTRIP# will go active and stay active until the processor has cooled down and a RESET# has been initiated."
The VR Down design guideline allows a Pentium 4 processor in the 478-pin package to decrease its voltage as amperage increases.