ассемблер – The presence of 9 bits in a byte in modern computers


An excerpt from Peter Abel's book:

A group of nine bits is a byte; eight bits of which contain data and one bit – parity.

Do current computers still use this? And is it possible to somehow influence it programmatically / use it (if any) or is it a purely machine part?


Not the fact that it is such an implementation.

But the principle itself: storing redundancy in order to detect (and possibly correct) errors – yes, it is still used in ECC RAM chips, used mainly on servers . Such memory is noticeably more expensive, slightly slower and must be supported by the motherboard and processor.

Implementation hardware : redundancy is considered a piece of iron. Correction if possible (one bit?) also happens in hardware, but the system is notified of the error (on x86 via machine check exception ) and can process the event programmatically at any level. If not possible, then only notification occurs.

Linux, for example, abruptly kills a process that used a page with dead memory and does not use this page again .

Ways to manually access redundant bits are unknown to me. I suspect that even if they exist, they are more likely for debugging purposes, and should not be used by end users.

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