The Intel Pentium 4 HT 651 was a desktop processor with 1 core, launched in January 2006. It is part of the Pentium 4 HT lineup, using the Cedar Mill architecture with Socket 775. Thanks to Intel Hyper-Threading the core-count is effectively doubled, to 2 threads. Pentium 4 HT 651 has 2 MB of L2 cache and operates at 3.4 GHz. Intel is building the Pentium 4 HT 651 on a 65 nm production process using 188 million transistors. The multiplier is locked on Pentium 4 HT 651, which limits its overclocking capabilities.
With a TDP of 86 W, the Pentium 4 HT 651 consumes a good deal of power, so decent cooling is needed. Intel's processor supports DDR1, DDR2 and DDR3 memory with a dual-channel interface. For communication with other components in the machine, Pentium 4 HT 651 uses a PCI-Express Gen 2 connection. Although the processor doesn't come with integrated graphics, certain motherboards with compatible chipsets can provide this capability.
The SSE4 instruction set is not supported, which can cause problems with modern games, as they require that capability.