UMA

UMA (Uniform Memory Access) is an architecture style that features a shared memory space that can be utilized in a uniform manner by any number of processing cores. In layman's terms this means that regardless of where that core resides, it will be able to directly access a memory location in the same time no matter how close the memory is. This style of architecture is also known as Symmetric Shared-Memory Multiprocessors or SMP in short.

The following image depicts how a UMA-style system would piece together. Each processor interfaces with a bus, which performs all of the memory accessing. Each processor added to this system increases the strain on the bus bandwidth, and thus we aren't able to scale it in quite the same way we could if we were to use a NUMA architecture:

The advantages of UMA are as follows:

• All RAM access takes the exact same amount of time
• Cache is coherent and consistent
• Hardware design is simpler

However, there is one disadvantage of UMA:

• UMA systems feature one memory bus from which all systems access memory; unfortunately, this presents scaling problems