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Re: Really compressed instruction streams

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quadibloc@invalid.com (John Savard) posted:

> On Thu, 24 Sep 2026 20:04:24 -0000 (UTC), Thomas Koenig
> <tkoenig@netcologne.de> wrote:
> 
> >It seems that the different CISC and compressed instruction sets
> >are ad-hoc (and not very good) attempts at compression of the
> >actual instructions that machines execute.
> 
> That's certainly true of the schemes I've been coming up with.
> 
> But since it takes so much time to fetch stuff from DRAM, some
> machines offer a mode where instructions are actually decrypted using
> a block cipher after being fetched!

I remember (I think) IBM compressing pages, but not cache lines.

> Given that, presumably the time cost of doing "real" compression on
> program code is not excessive.

Once you have the HW budget, LemplZiv is quite efficient.

> So, why doesn't anyone do this?

Big memory became cheap enough; disks (and SSDs) became big enough.
Also I/O busses became fast enough that saving 40% memory cycles no 
longer paid off, once SW had to read the stuff in and convert it.

>                                 I can think of many reasons why such a
> scheme could cause agony... but I also see a simple, plain
> alternative.

> Why not just have a compressed disk format for executable files in an
> operating system? Unpack them into conventional format when loading
> them into memory.

How do you page the code directly from the disk into executable memory ?

>                   That saves space where it is more doable, where the
> programs are lying idle, so they can be compressed with context
> obtained from their whole length.

Programs lying idle can rest on the disk in memory format.
 
> It doesn't achieve as much, but it avoids all the branching headaches.
> 
> John Savard

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Thread

Really compressed instruction streams Thomas Koenig <tkoenig@netcologne.de> - 2026-09-24 20:04 +0000
  Re: Really compressed instruction streams MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-09-24 22:17 +0000
    Re: Really compressed instruction streams BGB <cr88192@gmail.com> - 2026-09-24 18:00 -0500
    Re: Really compressed instruction streams scott@slp53.sl.home (Scott Lurndal) - 2026-09-25 14:39 +0000
      Re: Really compressed instruction streams cross@spitfire.i.gajendra.net (Dan Cross) - 2026-09-25 20:53 +0000
      Re: Really compressed instruction streams antispam@fricas.org (Waldek Hebisch) - 2026-10-05 23:10 +0000
        Re: Really compressed instruction streams John Levine <johnl@taugh.com> - 2026-10-06 02:46 +0000
  Re: Really compressed instruction streams quadibloc@invalid.com (John Savard) - 2026-09-24 22:37 +0000
    Re: Really compressed instruction streams MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-09-25 00:37 +0000
      Re: Really compressed instruction streams scott@slp53.sl.home (Scott Lurndal) - 2026-09-25 14:42 +0000
  Re: Really compressed instruction streams Robert Finch <robfi680@gmail.com> - 2026-09-24 20:56 -0400
    Re: Really compressed instruction streams Thomas Koenig <tkoenig@netcologne.de> - 2026-09-25 18:56 +0000
  Re: Really compressed instruction streams Michael S <already5chosen@yahoo.com> - 2026-09-25 11:54 +0300
    Re: Really compressed instruction streams Thomas Koenig <tkoenig@netcologne.de> - 2026-09-25 15:05 +0000
  Re: Really compressed instruction streams Michael S <already5chosen@yahoo.com> - 2026-09-25 17:39 +0300
  Re: Really compressed instruction streams Stefan Monnier <monnier@iro.umontreal.ca> - 2026-09-25 11:46 -0400
    Re: Really compressed instruction streams BGB <cr88192@gmail.com> - 2026-09-25 16:09 -0500
      Re: Really compressed instruction streams MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-09-25 22:59 +0000
        Re: Really compressed instruction streams BGB <cr88192@gmail.com> - 2026-09-25 18:51 -0500
          Re: Really compressed instruction streams scott@slp53.sl.home (Scott Lurndal) - 2026-09-28 15:26 +0000
            Re: Really compressed instruction streams BGB <cr88192@gmail.com> - 2026-09-28 17:42 -0500
      Re: Really compressed instruction streams BGB <cr88192@gmail.com> - 2026-09-26 03:21 -0500
    Re: Really compressed instruction streams Paul Clayton <paaronclayton@gmail.com> - 2026-09-27 21:12 -0400
      Re: Really compressed instruction streams BGB <cr88192@gmail.com> - 2026-10-01 15:42 -0500

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