R800 Creator

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By erpirao

Paladin (832)

erpirao's picture

15-12-2017, 22:25

I first apologize for my English on Google
from what I have read out there, the z800 was not completely discarded, it was reconverted into the z280, which follows a line of performance very different from the z180 / z380.

The Zilog Z280 was a 16-bit microprocessor, an enhancement of the Zilog Z80 architecture, introduced in July 1987. It was the Z800, renamed, with slight improvements such as being manufactured in CMOS. [1] It was a commercial failure. Zilog added to memory management unit (MMU) to expand the addressing range to 16 MB, features for multitasking and multiprocessor and coprocessor configurations, to 256-byte cache, and to a huge number of new instructions and addressing modes (giving a total of over 2000 combinations). Its internal clock signal can be configured to run at 1, 2 or 4 times the external clock's speed (e.g. at 12MHz CPU with a 3 MHz bus). More successful extensions of the Z80-architecture include the Hitachi HD64180 in 1986 and Zilog eZ80 in 2001, among others. See further Zilog Z800.

z280 wikipedia

I personally think that the R800 should have been mounted with all its features enabled, including the memory of 20 or 24? bits, DMA and improvements that were not used.

By Edevaldo

Expert (113)

Edevaldo's picture

18-12-2017, 07:07


From what I’ve seen, Z80 instruction set is very similar in terms of structure and complexity (and history) to x86. So if the Z80 evolution had continued today, I think it would’ve looked very similar to modern x86 processors.

It certainly would. My comment was in the sense that a low end 32-bit RISC of today has a much simpler design than the z80 had. If you take micro-controllers of today, the ones based on Risc cores and the ones still based on old 8-bit designs, the areas the CPUs occupy in silicon is very comparable. Despite a usual performance gap >8x per bus transaction (>25x if you think clock cycles). And among the 8-bits the Z80 is particularly complex.

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