Tube🌿Timeso i have picked up an INS8900D, also known as the National Semiconductor PACE. it is the first commercial 16-bit microprocessor. let's take it for a spin!
according to the datasheet, it is an NMOS device, and it requires three power supply voltages: 5V, 12V (!) and -8V (!!). the 5V supply is for the IO, the 12V supply is for the core voltage, and the -8V supply is the substrate bias.
🇺🇦 haxadecimal 🚫👑@tubetime +12V was common for early NMOS, before depletion loads, but usually Vgg (before substrate bias generators) was -5V. Oddball Vgg voltages were sometimes specified in order to have better performance or better margins. A few chips, even in production (!) had a Vgg value determined by production test hand-written on the IC package!