- Down to the silicon: how the Z80’s registers are implemented (righto.com)
The 8-bit Z80 microprocessor is famed for use in many early personal computers such the Osborne 1, TRS-80, and Sinclair ZX Spectrum. The Z80 has an innovative design for its internal registers, with two sets of general-purpose registers. The diagram below shows a highly-magnified photo of the Z80 chip, from the Visual 6502 team. Zooming in on the register file at the right, the transistors that make up the registers are visible (with difficulty). Each register is in a column, with the low bit on top and high bit on the bottom. This article explains the details of the Z80’s register structure: its architecture, how it works, and exactly how it is implemented, based on my reverse-engineering of the chip.
- Mount Persis (Wikipedia)
Mount Persis is a 5,464-foot (1,665-metre) summit located in Snohomish County, of Washington state. The mountain is part of the Cascade Range and is situated in the Mount Baker-Snoqualmie National Forest. The mountain was named for Persis Gunn (1846–1898), wife of homesteader/miner Amos Gunn who started the nearby town of Index, Washington, and also named nearby Mount Index. Precipitation runoff from the mountain drains into tributaries of the Skykomish River. Topographic relief is significant as the summit rises 4,160 feet (1,270 meters) above Anderson Creek in 0.8 mile (1.3 km). The rocks of Mount Persis are volcanic in origin and are considered amongst some of the earliest expressions of volcanism in the Cascade Mountain range in Washington.