The Parallax SX line of microcontrollers were formerly made by Ubicom. The SX dies are still manufactured by Ubicom, who sends them to Parallax for packaging. Ubicom used to make SX processor with 18, 20, 28, 48 and 52 pins, but because Parallax did not have packages for 18 and 52 pins chips the SX-18 and SX-52 have been discontinued.

The Parallax's SX series microcontrollers are 8-bit RISC microcontrollers (using a 12-bit instruction word) which have an unusually high speed, up to 75 MHz (75 MIPS), and a high degree of flexibility. They include up to 4096 12-bit words of Flash memory and up to 262 bytes of random access memory, an eight bit counter and other support logic. They are especially geared toward the emulation of I/O hardware in software, which makes them very flexible. While Parallax's SX micros are limited in variety, their high speed and additional resources allow programmers to create 'virtual devices', including complete video controllers, as required. For example there are software library modules to emulate I2C and SPI interfaces, UARTs, frequency generators, measurement counters and PWM and sigma-delta A/D converters. Other interfaces are relatively easy to write, and existing modules can be modified to get new features.

The Sx-Key is produced by Parallax and used to program the SX Microcontroller and then debug it. There is also a cheaper version called the SX-Blitz that does not contain a debugger. Currently, the most cost effective way of getting this device and being able to use it is to purchase a kit from Parallax (the only distruibuter of SX microcontrollers). The "SX Tech Tool Kit LITE" contains an SX-key, how-to book, prototype board, (2) microcontrollers, serial cable, and (2) resonators for an extra $20.

The well known programmer and author Andre LaMothe has proven that the SX-52 can actually be clocked to 80 MHz (80 MIPS) even though the specs say 75 MHz is the maximum. He has used the SX-52 in thousands of XGameStation game development computers all running at 80 MHz. He uses the speed and flexibility of the SX-52 chip to create a device with which a user can create their own Video game system. Some users have referred to these microcontrollers as PICs on steroids.