In mid-2001, Intel released the Foster core, which was also based on NetBurst, thus switching the Xeon CPUs to the new architecture as well.
Hyper-threading is Intel's proprietary simultaneous multithreading (SMT) implementation used to improve parallelization of computations (doing multiple tasks at once) performed on x86 processors.
[3] In reality, the longer pipeline resulted in reduced efficiency through a lower number of instructions per clock (IPC) executed as high enough clock speeds were not able to be reached to offset lost performance due to larger than expected increase in power consumption and heat.
The reason behind this is to generally make up for the low IPC count; additionally this considerably enhances the integer performance of the CPU.
Intel also replaced the high-speed barrel shifter with a shift/rotate execution unit that operates at the same frequency as the CPU core.
An example is shift and rotate operations, which suffer from the lack of a barrel shifter which was present on every x86 CPU beginning with the i386, including the main competitor processor, Athlon.
The Prescott core was produced on a 90 nm process, and included several major design changes, including the addition of an even larger cache (from 512 KB in the Northwood to 1 MB, and 2 MB in Prescott 2M), a much deeper instruction pipeline (31 stages as compared to 20 in the Northwood), a heavily improved branch predictor, the introduction of the SSE3 instructions, and later, the implementation of Intel Extended Memory 64 Technology (EM64T), Intel's branding for their compatible implementation of the x86-64 64-bit version of the x86 microarchitecture (as with hyper-threading, all Prescott chips branded Pentium 4 HT have hardware to support this feature, but it was initially only enabled on the high-end Xeon processors, before being officially introduced in processors with the Pentium trademark).
Power consumption and heat dissipation also became major issues with Prescott, which quickly became the hottest-running, and most power-hungry, of Intel's single-core x86 and x86-64 processors.
The fastest-clocked desktop Pentium 4 processors (single-core) had TDPs of 115 W, compared to 88 W for the fastest clocked mobile versions.