This chip has at least four revisions, first as a surface mounted chip labeled "MARIO CHIP 1" (Mathematical, Argonaut, Rotation & I/O), commonly called the Super FX, in the earliest Star Fox (1993) cartridges. From 1994, some boards have an epoxy version, and later a first revision is labeled GSU-1. Both versions are clocked with a 21.47 MHz signal, but an internal clock speed divider halves it to 10.74 MHz on the MARIO CHIP 1. The GSU-1 however runs at the full 21.47 MHz. Both the MARIO CHIP 1 and the GSU-1 can support a maximum ROM size of 8 Mbits. The design was revised to the GSU-2, which is still 16-bit, but this version can support a ROM size greater than 8 Mbit. The final known revision is the GSU-2-SP1. All versions of the Super FX chip are functionally compatible in terms of their instruction set. The differences are in packaging, pinout, maximum supported ROM size, and internal clock speed.[3]