In computer circles, stands for Non Uniform Memory Architecture, it is a MIMD type of machine. An SMP computer has one central memory and is a Uniform Memory Architecture, in that every processor has the same access to memory (which is why it's called symmetric). A NUMA machine has several processors, each with their own memory and the ability to talk to one another's memory. However, the ability to do so is non-uniform. Usually it is non-uniform in that it is not direct, as fast, and of as high of a priority. Whereas it is fairly easy to balance loads on an SMP machine, it is not so on a NUMA machine. Things such as locality of data and "promiscuity" of data must be taken in to account. The first NUMA machine was the Cm*, which was made 50 lsl-11 microprocessors. Should caching on remote memory be used, it is called ccNUMA.