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From: Lawrence D'Oliveiro <ldo@nz.invalid>
Newsgroups: comp.arch
Subject: Re: ancient OS history, ARM is sort of channeling the IBM 360
Date: Sat, 29 Jun 2024 23:53:59 -0000 (UTC)
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On Sat, 29 Jun 2024 18:22:04 -0000 (UTC), John Levine wrote:

> ... more often than not locate I/O is faster and easier.

Given all the caveats and restrictions, “easier” is not how I would 
describe it.

But perhaps we’re talking at cross-purposes. If Mitch did his TSS and PL/I 
stuff in the 1970s, while you’re talking about the 1960s, then that could 
explain it. By the 1970s, CPU/RAM speeds had improved to the point where 
copying records a few hundred bytes at a time between buffers was not the 
performance bottleneck; disk I/O was.

> When you touched the address, the page fault caused the I/O.

There seems to be this assumption that the paging mechanism is some kind 
of clever way of doing I/O. It’s not.