Groups > alt.folklore.computers > #234438

Re: Self-hosting and the 6502

From	cross@spitfire.i.gajendra.net (Dan Cross)
Newsgroups	alt.folklore.computers
Subject	Re: Self-hosting and the 6502
Date	2026-03-30 14:25 +0000
Organization	PANIX Public Access Internet and UNIX, NYC
Message-ID	<10qe15h$aq3$3@reader2.panix.com> (permalink)
References	<10qdbas$2991c$1@dont-email.me> <10qdsqr$2fj63$1@dont-email.me>

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In article <10qdsqr$2fj63$1@dont-email.me>, Lev <thresh3@fastmail.com> wrote:
>You're right on the terminology. The 6502 case is emulation,
>not virtualization - there's no hardware trap-and-emulate cycle,
>just a software interpreter running instructions one at a time.
>VM/370 does actual virtualization because the 370 architecture
>was designed with it in mind (SIE instruction, shadow page tables).
>
>The point I find interesting is that on the 6502, someone went
>ahead and wrote a software interpreter for an architecture that
>was already the thing doing the interpreting. No practical reason.
>The DEC approach of just building a proper multiuser OS was obviously
>the sane engineering choice, but nobody writes about it on hobbyist
>sites thirty years later because sanity doesn't stick in memory
>the way the ridiculous does.

Writing a proper multitasking OS usually requires some mechanism
to protect the OS itself from errant user programs; this implies
harwdare mechanisms that just don't exist on the 6502.

>Thanks for the correction on TOPS. I'd been unclear on whether
>the PDP-10 timesharing was doing anything VM-like under the hood
>or if it was straightforwardly process-isolated.

I don't know what the troll wrote about TOPS-10 and/or TOPS-20;
I plonked him years ago.  However, take whatever he said with a
large grain of salt: it's probably not true, or half-baked even
if there's a nugget of truth in there.

With respect to TOPS-20, however, it included a thing called
PA1050, one might reasonably call a type 2 hypervisor for
TOPS-10 programs, though it's closer to WINE in how it works: in
particular, it did not boot TOPS-10 (which, despite the name, is
totally different from and shares essentially no code with,
TOPS-20) but rather allowed one to execute TOPS-10 _programs_ on
TOPS-20 by trapping monitor calls and reflecting those back to
the PA1050 userspace program, which emulated the calls using
native TOPS-20 facilities.  Come to think of it, it's very
similar to how gVisor works.

	- Dan C.

Thread

Self-hosting and the 6502 Lev <thresh3@fastmail.com> - 2026-03-30 01:16 +0000
  Re: Self-hosting and the 6502 Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-03-30 06:12 +0000
    Re: Self-hosting and the 6502 thresh3@fastmail.com (Lev) - 2026-03-30 07:07 +0000
      Re: Self-hosting and the 6502 Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-03-30 08:13 +0000
        Re: Self-hosting and the 6502 thresh3@fastmail.com (Lev) - 2026-03-30 13:11 +0000
          Re: Self-hosting and the 6502 cross@spitfire.i.gajendra.net (Dan Cross) - 2026-03-30 14:25 +0000
            Re: Self-hosting and the 6502 Peter Flass <Peter@Iron-Spring.com> - 2026-03-30 07:40 -0700
              Re: Self-hosting and the 6502 Bob Eager <news0009@eager.cx> - 2026-03-30 17:02 +0000
                Re: Self-hosting and the 6502 cross@spitfire.i.gajendra.net (Dan Cross) - 2026-03-31 21:35 +0000
                Re: Self-hosting and the 6502 Bob Eager <news0009@eager.cx> - 2026-03-31 22:31 +0000
                Re: Self-hosting and the 6502 cross@spitfire.i.gajendra.net (Dan Cross) - 2026-04-01 10:44 +0000
                Re: Self-hosting and the 6502 Bob Eager <news0009@eager.cx> - 2026-04-01 10:47 +0000
                Re: Self-hosting and the 6502 cross@spitfire.i.gajendra.net (Dan Cross) - 2026-04-01 13:57 +0000
              Re: Self-hosting and the 6502 cross@spitfire.i.gajendra.net (Dan Cross) - 2026-03-31 21:34 +0000
                Re: PC/IX, was Self-hosting and the 6502 John Levine <johnl@taugh.com> - 2026-04-01 02:01 +0000
              Re: Self-hosting and the 6502 "Kurt Weiske" <kurt.weiske@realitycheckbbs.org.remove-a96-this> - 2026-04-02 07:35 -0700
            Re: Self-hosting and the 6502 jayjwa <jayjwa@atr2.ath.cx.invalid> - 2026-04-01 18:14 -0400
              Re: Self-hosting and the 6502 cross@spitfire.i.gajendra.net (Dan Cross) - 2026-04-01 22:56 +0000
                Re: Self-hosting and the 6502 Rich Alderson <news@alderson.users.panix.com> - 2026-04-01 21:44 -0400
                Re: Self-hosting and the 6502 Peter Flass <Peter@Iron-Spring.com> - 2026-04-01 21:35 -0700
          Re: Self-hosting and the 6502 Nuno Silva <nunojsilva@invalid.invalid> - 2026-03-30 15:25 +0100
            Re: Self-hosting and the 6502 Peter Flass <Peter@Iron-Spring.com> - 2026-03-30 07:42 -0700
          Re: Self-hosting and the 6502 Gordon Henderson <gordon+usenet@drogon.net> - 2026-04-01 11:43 +0000
            Self-hosting and the PDP-10 [was Re: Self-hosting and the 6502] Rich Alderson <news@alderson.users.panix.com> - 2026-04-01 15:41 -0400
              Re: Self-hosting and the PDP-10 [was Re: Self-hosting and the 6502] cross@spitfire.i.gajendra.net (Dan Cross) - 2026-04-01 22:16 +0000
                Re: Self-hosting and the PDP-10 [was Re: Self-hosting and the 6502] Rich Alderson <news@alderson.users.panix.com> - 2026-04-01 21:51 -0400
                Re: Self-hosting and the PDP-10 [was Re: Self-hosting and the 6502] Peter Flass <Peter@Iron-Spring.com> - 2026-04-01 21:37 -0700
                Re: Self-hosting and the PDP-10 [was Re: Self-hosting and the 6502] cross@spitfire.i.gajendra.net (Dan Cross) - 2026-04-02 10:50 +0000
                Re: Self-hosting and the PDP-10 [was Re: Self-hosting and the 6502] Rich Alderson <news@alderson.users.panix.com> - 2026-04-02 15:18 -0400
                Re: Self-hosting and the PDP-10 [was Re: Self-hosting and the 6502] cross@spitfire.i.gajendra.net (Dan Cross) - 2026-04-03 13:13 +0000
                Re: Self-hosting and the PDP-10 [was Re: Self-hosting and the 6502] cross@spitfire.i.gajendra.net (Dan Cross) - 2026-04-02 10:58 +0000
                Re: Self-hosting and the PDP-10 [was Re: Self-hosting and the 6502] Peter Flass <Peter@Iron-Spring.com> - 2026-04-02 07:32 -0700
                Re: Self-hosting and the PDP-10 [was Re: Self-hosting and the 6502] cross@spitfire.i.gajendra.net (Dan Cross) - 2026-04-02 18:23 +0000
      Re: virtualization, Self-hosting and the 6502 John Levine <johnl@taugh.com> - 2026-03-30 16:28 +0000
    Re: Self-hosting and the 6502 Bill Findlay <findlaybill@blueyonder.co.uk> - 2026-03-30 17:59 +0100
      Re: Self-hosting and the 6502 Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-03-30 21:24 +0000
  Re: Self-hosting and the 6502 cross@spitfire.i.gajendra.net (Dan Cross) - 2026-03-30 14:16 +0000
    Re: Self-hosting and the 6502 Peter Flass <Peter@Iron-Spring.com> - 2026-03-30 07:35 -0700
      Re: emulation, virtualization, Self-hosting and the 6502 John Levine <johnl@taugh.com> - 2026-03-30 16:39 +0000
        Re: emulation, virtualization, Self-hosting and the 6502 ted@loft.tnolan.com (Ted Nolan <tednolan>) - 2026-03-30 17:20 +0000
          Re: emulation, virtualization, Self-hosting and the 6502 cross@spitfire.i.gajendra.net (Dan Cross) - 2026-03-31 23:39 +0000
            Re: emulation, virtualization, Self-hosting and the 6502 scott@slp53.sl.home (Scott Lurndal) - 2026-04-02 14:57 +0000
              Re: emulation, virtualization, Self-hosting and the 6502 rbowman <bowman@montana.com> - 2026-04-02 18:04 +0000
                Re: emulation, virtualization, Self-hosting and the 6502 scott@slp53.sl.home (Scott Lurndal) - 2026-04-02 18:45 +0000
      Re: Self-hosting and the 6502 David Wade <g4ugm@dave.invalid> - 2026-03-30 18:03 +0100
      Re: Self-hosting and the 6502 Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-03-30 21:23 +0000
      Re: Self-hosting and the 6502 cross@spitfire.i.gajendra.net (Dan Cross) - 2026-03-31 23:05 +0000
    Re: Self-hosting and the 6502 John Ames <commodorejohn@gmail.com> - 2026-03-30 07:57 -0700
      Re: Self-hosting and the 6502 cross@spitfire.i.gajendra.net (Dan Cross) - 2026-03-30 22:19 +0000
        Re: Self-hosting and the 6502 Nuno Silva <nunojsilva@invalid.invalid> - 2026-03-31 00:18 +0100
          Re: Self-hosting and the 6502 cross@spitfire.i.gajendra.net (Dan Cross) - 2026-03-31 22:04 +0000
    Re: Self-hosting and the 6502 Bob Eager <news0009@eager.cx> - 2026-03-30 17:07 +0000
  Re: Self-hosting and the 6502 antispam@fricas.org (Waldek Hebisch) - 2026-03-31 03:34 +0000
    Re: Self-hosting and the 6502 Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-03-31 03:54 +0000
      Re: Self-hosting and the 6502 antispam@fricas.org (Waldek Hebisch) - 2026-03-31 05:01 +0000
    Re: Self-hosting and the 6502 Lev <thresh3@fastmail.com> - 2026-03-31 05:26 +0000
    Re: Self-hosting and the 6502 Peter Flass <Peter@Iron-Spring.com> - 2026-03-31 07:48 -0700
      Re: machine simulation, Self-hosting and the 6502 John Levine <johnl@taugh.com> - 2026-03-31 18:06 +0000
    Re: Self-hosting and the 6502 scott@slp53.sl.home (Scott Lurndal) - 2026-03-31 15:03 +0000
    Re: Self-hosting and the 6502 Bill Findlay <findlaybill@blueyonder.co.uk> - 2026-03-31 18:23 +0100
      Re: Self-hosting and the 6502 Peter Flass <Peter@Iron-Spring.com> - 2026-03-31 13:04 -0700

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