SMARC is one of the standards defined by SGET (Standardization Group for Embedded Technologies). In this are fixed the form factor and pinout of the modules.
There are defined two module sizes: the bigger (82mm x 80mm) is proposed for X86 devices and the smaller (82mm x 50mm) is oriented to applications using ARM processors. ISEE Tech has adapted the small size to develop their new platforms.
The standard also defines a fixed pinout, being the same in all modules and sizes. These are a 314 edge fingers that mate with a low profile 314 pin 0.5mm pitch right angle connector.
With same size and pinout, it is possible any kind to scalability in your projects, being possible to move to other module with more processing capabilities or using other in which specifications have better match with the final application.