Looking at the specs for the TI TMS9900, Zilog Z80, and the MOS 6502, the TI chip came in a 64-pin DIP and required +5V, -5V, and +12V power supply while the ot

Looking at the specs for the TI TMS9900, Zilog Z80, and the MOS 6502, the TI chip came in a 64-pin DIP and required +5V, -5V, and +12V power supply while the other two chips came in a 40 pin DIP package and only required a +5V power supply. The 6502 was cheap (<$30), the Z80 was more expensive at introduction, but looking at price lists, dropped down close to the same price as the 6502 within a few years. from https://www.cpushack.com/2015/02/05/ti-tms9900sbp9900-accidental-success/ https://www.cpushack.com/2015/02/05/ti-tms9900sbp9900-accide...: " In 1978 a 9980 cost $30 while a TMS9900 cost $70." Also, in the comments from the above link: "Many years later, the processor architect for the TMS9995 (Karl Guttag) pointed out to me that whatever context switch benefits the WP offered were quickly outweighed by the required memory access cycles only a handful of instructions into an interrupt service routine. It was a false economy."