In order to fit into very limited thermal constraints and power consumption, the Intel® Core™ Duo processor has a derivative that contains a single core only. This can be achieved by either disabling one of the cores either at the OS level or as a BIOS option, or at the architecture level, where one core is disconnected from the power grid.

The first option is a user or OS decision. If you run a single-core OS on an Intel® Core™ Duo system, it will keep the second core idle, at CC4 sleep state. Please note that due to the way the BIOS is set, each time an interrupt is received or a broadcast IPI is sent, this core may need to wake up and go immediately back to a sleep state, consuming small amounts of dynamic power.

The user can disable the second core via a BIOS option as well. In this case, the system does not recognize the other core and so it is kept in CC4 state all the time, consuming no dynamic power at all.

The disadvantage of the two methods described above is that the core still consumes static power. In order to avoid this and reduce the power consumption of the core even further, Intel introduces the single-core version of Intel® Core™ Duo technology, called Intel® Core™ Solo processor, which disconnects the non-active core from the power grid, or saves the area and does not fabricate this part at all.