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I understand the purpose of the pf flag, which is to indicate whether there are an even or odd number of ones in the resulting data after certain instructions manipulate the register. However, It is certainly not just for programming tricks such as using assembly to replace several shifts and XOR operations in C, or for loops. There must be a specific intention behind it.

I couldn't find any relevant information by searching on Google either, and it's possible that the keywords I used were not accurate. I also didn't come across any similar questions on Stack Overflow.

Peter Cordes
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Michael Coleman
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    Believe it or not, the actual design decision in 1967 to add PF to 8008 (released in 1972, years before 8086 which later evolved out of it) apparently *was* a performance optimization for an early serial-port parity-checking use-case which wasn't running as fast as the engineers wanted it to. [An answer](https://stackoverflow.com/a/75739896/224132) is directly from a journalist who interviewed Victor Poor about 286 years later, and said this subject came up. – Peter Cordes May 17 '23 at 03:56
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    (Perhaps you weren't aware that parity bits were a real thing used on the wire in serial port protocols, before later stuff like per-packet checksums. So it's not that weird for an early CPU to have it in hardware. And x86 has been accumulating baggage since forever, maintaining backwards compat with 8086, which in turn was designed for easy source porting from 8080, which in turn had 8008 roots. [The start of x86: Intel 8080 vs Intel 8086?](https://retrocomputing.stackexchange.com/q/6500)) – Peter Cordes May 17 '23 at 03:57

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