The TI-84 Plus CE, at least, uses the same CPU as my board (plus or minus revisions) - but it clocks it _much_ lower, at 15MHz. The eZ80 uses around 30mA at tha

The TI-84 Plus CE, at least, uses the same CPU as my board (plus or minus revisions) - but it clocks it _much_ lower, at 15MHz. The eZ80 uses around 30mA at that speed; it also has a sleep mode using under 3µA that I would expect a battery powered device to make heavy use of. The Z84C00 at 6Mhz will also "only" use around 30mA, down to 10µA in standby. At 15MHz the Z84C00 uses something more like 80mA, though, so the "turbo" mode in that calculator line probably chews through batteries. I expect TI still uses the eZ80 CPU for the same reason other companies still use Z80-based processors - backwards compatibility. The Z80's got a very long life in industrial control systems, where you want to avoid rewriting the code if you reasonably can. The eZ80 is about as modernised as you can take the Z80 core, but as you say a lot of the Z80 design is due to the constraints of the era. It was also designed to be code compatible with the Intel 8080, and probably would have just quietly fizzled on launch if it didn't have that.