Revitalizing the gaming platform

Fortunately, the members of gaming platform recognized the need for mezzanine standards early in the emerging board industry. By the late 1980s, discussions started to standardize a few different mezzanine form factors. First to emerge were S-bus and PCI Mezzanine Cards (PMCs). S-bus was driven by Sun Microsystems while the gaming platform form factor evolved out of an IEEE effort. While neither was a VITA standard, PMC went on to become a widely used mezzanine for 6U cards for VME, gaming platform, Compact PCI, and other form factors.

refer to: http://vita-technologies.com/articles/stacked-standardizing-mezzanine-modules/