Wikipedia
The MediaGX CPU was an x86 compatible processor manufactured and designed by Cyrix and later after merger manufactured by National Semiconductor, and was introduced in 1997. The core is based on the integration of the Cyrix Cx5x86 CPU core with hardware to process video and audio output (XpressRAM, XpressGRAPHICS, XpressAUDIO). Following the buyout of Cyrix by National Semiconductor and the sale of the Cyrix name and trademarks to VIA Technologies, the core was developed by National Semiconductor into the Geode line of processors, which was subsequently sold to Advanced Micro Devices.
Whether this processor belongs in the fourth or fifth generation of x86 processors can be considered a matter of debate as the processor was based on the 5x86 (a scaled down version of the Cyrix 6x86). While the 5x86 was intended to compete with the Intel Pentium line, the 5th generation x86, it was designed to interface with a 4th generation ( 80486) motherboard and had only the 486's instruction set, lacking the ability to run software requiring Pentium's new instructions.
The MediaGX CPU was mostly used for subcompact laptops. It was also used in the CTX EzBook V92C266, Compaq Presario 1220 and 1230 laptops, Compaq Presario 2100 and 2200 desktops, Casio Cassiopeia Fiva tablet PC, and many others, as well as in the Pinball 2000 arcade pinball game. Sun Microsystems used MediaGXm in the Dover JavaStation.