A dual processor motherboard is a computer motherboard that has space for two complete and separate processor chips. These chips are then connected together on-board using a number of different methods, although a specialized processor bus system is most common. In theory, these machines have the potential to operate at speeds far beyond a normal computer, as the individual processors provide a near doubling in power. While dual processor motherboards have always been uncommon, with the advent of multicore processors, they are even harder to find.
Generally, a dual processor motherboard requires two of the same processors. They need to be exactly the same, or the imbalance causes the computer to become unstable and shut down. While this is the case nearly every time, there have been boards that could take slightly different processors, but these were exceptionally rare.
This style of motherboard was common among high-end desktop and low-end server systems. In most cases, only high-end desktop systems could accept the hardware and software required to utilize the power of the second processor. On the server side, mid- to high-range servers often switched away from the standard motherboard route into other types of systems like rackmount or blade systems.
The physical design of a dual processor motherboard often varies from a standard motherboard. The second processor changes the basic layout of the system, typically by displacing the memory. This pushes the memory down the board, often displacing the chipset towards the expansion slots. As a result of these alterations, a dual processor motherboard will typically have less expansion slots than a similar-sized motherboard.
While a dual processor motherboard seems like it would make a system twice as fast as a standard computer, this is not the case. Limitations on the processor’s access to the system bus and memory will often require one processor to wait while the other is active. In addition, until recently, few programs were written to take advantage of a multiprocessor system. Most programs will access the main processor and never send anything to the second; it was often limited to operating system processes on all but the most powerful of programs.
With the advent of multicore processors, many of the drawbacks to a dual processor motherboard have gone away. The process of allocating system resources has been changed to allow more even access, and there are more programs that will use a second processor. In fact, many programs are now written to use multiple processors at the same time.
For all this innovation, the dual processor motherboard is still an oddity. Since multicore processors can do the same thing as a dual system without many of the technical problems, they took over the market. Finally, when the common multicore exceeded two processor cores, it surpassed the power of a basic dual processor system.