Nostalgia.
Intel is the most famous. Most of the chip companies in Silicon Valley can trace their roots back to Fairchild (including Zilog, AMD, National Semiconductor, Maxim)
The Z80, for a long time a very very popular microprocessor was descended from the Intel 8080 and the Intel 8085. Zilog was started by someone from Intel. I heard the Z80 opcodes made a lot of sense if you looked at them in octal rather than hexadecimal. The Z80 is also the classic 8bit CISC micro-processor; it had instructions would could do block copies and searches, for instance.
13. What was good about 6502 architecture? Why didn't it scale well?
At a time when CPU's had few transistors, few registers and memory was faster than CPU's, it had a fast index mode (8-bit indexed addressing) so the first 256 bytes of memory could be used effectively as a large register file. ... But as CPU's got much faster than memory, going off chip more than absolutely necessary is a bad idea.
TI did a similar thing with their 9900 architecture. The register file was actually in memory. It also had a kind of context jump which got you a new set of registers. It also didn't have a stack, instead storing return addresses in registers. This required some interesting and creative techniques for modular code. The 9900 also had an extremely well-organized instruction set.
Wade.
