Where Is the CPU Located on a Computer?
Though seemingly unintentional, the placement of a central processing unit (CPU) on a motherboard is a strategical design choice made by manufacturers for various reasons. Most notably, CPU cooling and internal device temperatures are taken into consideration when deciding the placement of a CPU on a motherboard.
The processor placement is not a requirement to be considered within the specifications of the advanced technology extended (ATX) form factor, or any other form factor for that matter. The processor is almost exclusively placed in the upper left to upper middle section of a motherboard. This placement is based on the assumption that it will be in an upright tower chassis, which will align the CPU with the rear exhaust fan and the power supply unit's cooling fan.
Due to the common thermal considerations taken into account by manufacturers when deciding CPU placement on a motherboard, the location of any CPU across the majority of all consumer-level motherboards has varied by a matter of 1 to 2 centimeters--maximum--in the last 20 years.
CPU placement on enterprise-level servers which are housed horizontally rather than vertically like consumer computers, can vary widely as there are fewer on-board devices to design around and a different thermal pattern to work with.
Placing the CPU in the upper area of a motherboard reduces the probability of other devices or their data and power cables from blocking the airflow to and from a CPU. The CPU is also a large heat source which would cause thermal damage to any wires or cables crossing over it for extended lengths of time.
Given the recent affordability and ever increasing widespread acceptance of liquid-cooled processors, it is possible in the near future that CPU placement will change drastically as liquid cooling systems remove far greater amounts of heat without spreading it around the inside of the computer's case as with air cooling. Thus, water cooling removes many restrictions imposed by thermal management from system designers.