On 03/30/2019 01:16 PM, D. Hugh Redelmeier via talk wrote:
If you already have 4-bit or 8-bit software which already does most of the job, or if you have engineers who already have deep skills only with those old processors, that might justify using old cores.
As a programmer who has dealt with 8-bit, 16-bit, 32-bit, and 64-bit processors, I can tell you that each step helped. The only negative of the larger systems is that they invited software bloat, and that bloat really could be a drag on productivity. OK, there is also hardware bloat: there usually were more complex mechanisms to actually get to the pins.
When you're cranking out millions of chips, real estate is a significant factor. With custom chips, the number of CPU pins is independent of how many leads leave the package. The chip is just a black box, with whatever CPU in it. There are still things for which 4 bits is sufficient.
Some of us cut our teeth programming on these things. Usually in assembly language. Many of us fall in love with the first system we deeply understood. So there is a generation of defenders of the z80 (and the 6502). This is nostalgia: they are indefensible for new designs.
My first CPU was the 8080, in my IMSAI 8080. I used to code directly into octal, on square ruled paper. ;) I then moved my coding skills to Data General Nova 800, followed by 6502 & 6809, the latter two for courses at Ryerson, the Nova at work.