Before Netbooks and mini PCs, there was the TMS9900, or in other words, Texas Instruments’ 990 minicomputer CPU. Basically, it “was designed as a single chip version of the TI 990 minicomputer series, much like the Intersil 6100 was a single chip PDP-8, and the Fairchild 9440 and Data General mN601 were both one chip versions of Data General’s Nova.”
One unique feature, though, was that all general purpose user registers were actually kept in external memory. A single workspace register (WP) pointed to the 16 register set (each register being 16 bits wide) in RAM, so when a subroutine was entered or an interrupt was processed, only the single workspace register had to be changed.
