Daily Archives: 2022-11-17

A secret Apple Silicon extension to accommodate an Intel 8080 artifact

Source: Hacker News

Article note: This is pretty cool, Apple has a mode to automatically compute the two 8080 arithmetic flags that ARMs don't. A setting enables computing the “adjust flag” (AF) and the “parity flag” (PF) exactly as an 8080-family part in bits 26 and 27 of the flags register. In combination with a setting to switch to x86 style memory ordering, it's suddenly much less surprising that Rosetta2 does such a good job compared to other x86-on-ARM schemes.
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