Intel is now becoming a victim of its decision to differentiate between low- and mid-end Pentium 4 Prescott's on the one hand and the more demanding versions at maximum clock speeds on the other. The so-called performance requirement bit or PRB (MSR_PLATFORM_BRV bit 18) is responsible for approving the usage of the processor's designated multiplier or a factory default one (which is x14). The latter was implemented for security reasons, as the requirements as well as thermal specifications of the two fastest P4s are much higher than for the mainstream models.