The MSX series of home computers followed a set of standards designed to make them interchangeable and easy to produce from "off-the-shelf" parts. It's been assumed that the "MSX" stands for "MircoSoft eXtended," since the initial design standards were first conceived and put into practice by a Microsoft Japan engineer named Kazuhiko Nishi, and the machines featured a built-in programming language designed by Microsoft. According to more recent interviews with Kazuhiko Nishi, however, the acronym was originally intended to represent "Machines with Software eXchangeability."
In addition to Microsoft, other electronics corporation supported MSX standards, and companies such as Sony, Sanyo, Philips, Spectravideo, and several others manufactured and sold their own versions of the computer. The MSX line became the default standard home computer system, in Japan and other Asian nations, throughout the later half of the 1980s. It's popularity also spread to places in Europe and South America, but it never posed a serious threat to the prevalence of Commodore and Apple systems in the United States. Four lines of MSX computers were produced: The original "MSX" (1983), the "MSX 2" (1986), the "MSX 2+" (1988), and the "MSX Turbo R" (1990).
Although production of MSX computers officially ceased in the mid-1990s, and many North Americans have never seen nor even heard of the machine, it is of special significance to gamers as the platform for many of the earliest home-version releases from Konami, including a unique edition of Castlevania (known as Vampire Killer) and the first two games in Hideo Kojima's Metal Gear series.
~ T.J. Deci, All Game Guide