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From: Terje Mathisen <terje.mathisen@tmsw.no>
Newsgroups: comp.arch
Subject: Re: Is Parallel Programming Hard, And, If So, What Can You Do About
 It?
Date: Mon, 12 May 2025 08:05:56 +0200
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Lawrence D'Oliveiro wrote:
> On Mon, 12 May 2025 00:30:37 +0000, MitchAlsup1 wrote:
>=20
>> On Sun, 11 May 2025 23:46:17 +0000, Lawrence D'Oliveiro wrote:
>>
>>> That=C3=A2=E2=82=AC=E2=84=A2s why we have memory caches.
>>
>> Which architects tend to only understand what happens when these cache=
s
>> are attached to CPUs and not "Joe Random Bus Master",
>=20
> One of my pet peeves is disk drives with memory caches in them. Why?
>=20

For reads it allows the disk to always read full sets of sectors, the=20
following blocks are likely to be needed soon anyway.

For writes, as long as the drive has enough energy (maybe in the form of =

spinning inertia, or a hefty cap?) the always be able to save the buffer =

cache to spinning rust, it can allow operations to complete immediately, =

or as soon as the data has been transferred into the disk cache.

Since all disks are using linear sector (or 4K block?) addressing these=20
days, instead of head/cylinder/sector, a little bit of cache can help=20
hide the tiny time glitches when the disk has to reposition.

Terje

--=20
- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"