The Intel Pentium 4 HT 561 was a desktop processor with 1 core, launched in June 2005. It is part of the Pentium 4 HT lineup, using the Prescott architecture with Socket 775. Thanks to Intel Hyper-Threading the core-count is effectively doubled, to 2 threads. Pentium 4 HT 561 has 1 MB of L2 cache and operates at 3.6 GHz. Intel is building the Pentium 4 HT 561 on a 90 nm production process using 125 million transistors. The multiplier is locked on Pentium 4 HT 561, which limits its overclocking capabilities.
With a TDP of 115 W, the Pentium 4 HT 561 consumes a lot of power, so good cooling is definitely 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 561 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.