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Self-hosting and the 6502

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  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

Page 2 of 4 — ← Prev page 1 [2] 3 4  Next page →

#234439

On 2026-03-30, Lev wrote:

> 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 [...]

Except on alt.folklore.computers? :-)

-- 
Nuno Silva

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#234442

On 3/30/26 07:25, Nuno Silva wrote:
> On 2026-03-30, Lev wrote:
> 
>> 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 [...]
> 
> Except on alt.folklore.computers? :-)
> 

Yup. The "official" IBM approach was TSS.

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#234534

In article <10qdsqr$2fj63$1@dont-email.me>, Lev <thresh3@fastmail.com> wrote:

>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.

Slightly related; My own "fantasy parallel universe" series of systems
does this - or did this as I was developing it.

I started on the 6502 wanting a "self hosting" system - not by making
it emulate itself, but meaning the abiltiy to develop and run programs
on the same hardware without resorting to cross compilation.

Fast forward and on to the 65816 (the bastard 16-bit version of the
6502) and I had decided BCPL was my language of choice and wrote a "VM"
for the product of the BCPL compiler - a bytecode called "cintcode". I
wrote an Os in BCPL and could edit, compile and run programs directly
on my little SBC.

It also handled multitasking - at the bytecode level.

Looking to the (fantasy) future, I decided 32-bits and RISC-V was the
next step so I wrote a RISC-V emulator in BCPL and ran it on my 65816
system. It ran well and I could externally compile and run little C
programs to test it, so I set about writing the cintcode VM in RISC-V
assembler.

Then I just fed it the binary version of my OS and booted it.

So now I had my OS running on a RISC-V emulator written in BCPL running
on an OS written in BCPL running on the '816. Turtles all the way, as may
be said.

It was slow but usable as a test bed before I found suitable actual
RISC-V hardware.

So a different sort of self-hosting to the main thread, but maybe
interesting none the less.. (And I have a deranged idea that if I were
to write a 65816 emulator in BCPL and emulate my original board then I
could boot my OS under that but maybe that's a rabbit hole too deep...

-Gordon

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#234550 — Self-hosting and the PDP-10 [was Re: Self-hosting and the 6502]

Gordon Henderson <gordon+usenet@drogon.net> writes:

  [ snip ]

> So now I had my OS running on a RISC-V emulator written in BCPL running on an
> OS written in BCPL running on the '816. Turtles all the way, as may be said.

> It was slow but usable as a test bed before I found suitable actual RISC-V
> hardware.

When XKL was developing their first product, code named "ToaD" = "10 on a desk",
the primary work was done on a DECSYSTEM-2065 running TOPS-20 v6.1 (which I
upgraded to v7.0 when I got there a couple of years later).

Because the Toad was an extended clone of the KL-10 processor, featuring full
30 bit addressing, changes needed to be made to TOPS-20 to support the memory
model in its full glory.

Ralph Gorin[*] wrote an emulator for the Toad in assembly language.  This executed
all instructions natively on the KL-10; the primary difference was that the
JSYS ("Jump to SYStem") instruction was assembled as an unused opcode rather
than the defined 104, so that the emulator program could use all the OS facilities
directly without interference from the emulated system.

Once we had working hardware, regression testing against the emulator had us up
and running in days rather than weeks.

[*] Ralph is of course the author of _Assembly Language Programming for the
    DECSYSTEM-20_, first edition published by Digital Press (a DEC subsidiary).
    Among other hats he wore in the startup phase of XKL was "Chief System Architect".

-- 
Rich Alderson					  news@alderson.users.panix.com
      Audendum est, et veritas investiganda; quam etiamsi non assequamur,
	  omnino tamen proprius, quam nunc sumus, ad eam perveniemus.
									--Galen

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#234559 — Re: Self-hosting and the PDP-10 [was Re: Self-hosting and the 6502]

In article <mddv7eampsr.fsf_-_@panix5.panix.com>,
Rich Alderson  <news@alderson.users.panix.com> wrote:
>Gordon Henderson <gordon+usenet@drogon.net> writes:
>
>  [ snip ]
>
>> So now I had my OS running on a RISC-V emulator written in BCPL running on an
>> OS written in BCPL running on the '816. Turtles all the way, as may be said.
>
>> It was slow but usable as a test bed before I found suitable actual RISC-V
>> hardware.
>
>When XKL was developing their first product, code named "ToaD" = "10 on a desk",
>the primary work was done on a DECSYSTEM-2065 running TOPS-20 v6.1 (which I
>upgraded to v7.0 when I got there a couple of years later).
>
>Because the Toad was an extended clone of the KL-10 processor, featuring full
>30 bit addressing, changes needed to be made to TOPS-20 to support the memory
>model in its full glory.

Rich, I think I've asked this before, but can't recall the
answer.  Is that monitor available publicly, outside of the XKL
Darkstar or other hardware?  30-bit addressing would be a nice
extension over the monitor in the Panda distribution.

	- Dan C.

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#234566 — Re: Self-hosting and the PDP-10 [was Re: Self-hosting and the 6502]

cross@spitfire.i.gajendra.net (Dan Cross) writes:

> In article <mddv7eampsr.fsf_-_@panix5.panix.com>,
> Rich Alderson  <news@alderson.users.panix.com> wrote:

>> When XKL was developing their first product, code named "ToaD" = "10 on a desk",
>> the primary work was done on a DECSYSTEM-2065 running TOPS-20 v6.1 (which I
>> upgraded to v7.0 when I got there a couple of years later).

>> Because the Toad was an extended clone of the KL-10 processor, featuring full
>> 30 bit addressing, changes needed to be made to TOPS-20 to support the memory
>> model in its full glory.

> Rich, I think I've asked this before, but can't recall the answer.  Is that
> monitor available publicly, outside of the XKL Darkstar or other hardware?
> 30-bit addressing would be a nice extension over the monitor in the Panda
> distribution.

The XKL monitor is a commercial product, available only with the purchase of
a compatible hardware system.

The Panda distribution is of course intended for a KL-10 compatible processor
(and was originally targeted at DEC hardware rather than simulator programs),
so it of course does not have the expanded data structures to allow a full
gigaword of memory.  Extending the monitor is left as an exercise for the reader.

-- 
Rich Alderson					  news@alderson.users.panix.com
      Audendum est, et veritas investiganda; quam etiamsi non assequamur,
	  omnino tamen proprius, quam nunc sumus, ad eam perveniemus.
									--Galen

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#234569 — Re: Self-hosting and the PDP-10 [was Re: Self-hosting and the 6502]

On 4/1/26 18:51, Rich Alderson wrote:
> cross@spitfire.i.gajendra.net (Dan Cross) writes:
> 
>> In article <mddv7eampsr.fsf_-_@panix5.panix.com>,
>> Rich Alderson  <news@alderson.users.panix.com> wrote:
> 
>>> When XKL was developing their first product, code named "ToaD" = "10 on a desk",
>>> the primary work was done on a DECSYSTEM-2065 running TOPS-20 v6.1 (which I
>>> upgraded to v7.0 when I got there a couple of years later).
> 
>>> Because the Toad was an extended clone of the KL-10 processor, featuring full
>>> 30 bit addressing, changes needed to be made to TOPS-20 to support the memory
>>> model in its full glory.
> 
>> Rich, I think I've asked this before, but can't recall the answer.  Is that
>> monitor available publicly, outside of the XKL Darkstar or other hardware?
>> 30-bit addressing would be a nice extension over the monitor in the Panda
>> distribution.
> 
> The XKL monitor is a commercial product, available only with the purchase of
> a compatible hardware system.
> 
> The Panda distribution is of course intended for a KL-10 compatible processor
> (and was originally targeted at DEC hardware rather than simulator programs),
> so it of course does not have the expanded data structures to allow a full
> gigaword of memory.  Extending the monitor is left as an exercise for the reader.
> 

I didn't know XKL was still in the business. I looked them up a while 
ago and they seemed to be selling networking hardware.

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#234570 — Re: Self-hosting and the PDP-10 [was Re: Self-hosting and the 6502]

In article <10qkrpq$qbu8$2@dont-email.me>,
Peter Flass  <Peter@Iron-Spring.com> wrote:
>On 4/1/26 18:51, Rich Alderson wrote:
>> cross@spitfire.i.gajendra.net (Dan Cross) writes:
>> 
>>> In article <mddv7eampsr.fsf_-_@panix5.panix.com>,
>>> Rich Alderson  <news@alderson.users.panix.com> wrote:
>> 
>>>> When XKL was developing their first product, code named "ToaD" = "10 on a desk",
>>>> the primary work was done on a DECSYSTEM-2065 running TOPS-20 v6.1 (which I
>>>> upgraded to v7.0 when I got there a couple of years later).
>> 
>>>> Because the Toad was an extended clone of the KL-10 processor, featuring full
>>>> 30 bit addressing, changes needed to be made to TOPS-20 to support the memory
>>>> model in its full glory.
>> 
>>> Rich, I think I've asked this before, but can't recall the answer.  Is that
>>> monitor available publicly, outside of the XKL Darkstar or other hardware?
>>> 30-bit addressing would be a nice extension over the monitor in the Panda
>>> distribution.
>> 
>> The XKL monitor is a commercial product, available only with the purchase of
>> a compatible hardware system.
>> 
>> The Panda distribution is of course intended for a KL-10 compatible processor
>> (and was originally targeted at DEC hardware rather than simulator programs),
>> so it of course does not have the expanded data structures to allow a full
>> gigaword of memory.  Extending the monitor is left as an exercise for the reader.
>
>I didn't know XKL was still in the business. I looked them up a while 
>ago and they seemed to be selling networking hardware.

They are and they do; the hardware (as I understand it) contains
a custom ASIC for the networking side, and a control processor
implemented on an FPGA that runs the modified TOPS-20 monitor
that Rich described.  I was hoping there was sufficient product
differentiation that they would (or could be persuaded to)
release just the monitor component, but alas: that appears to be
unlikely.

	- Dan C.

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#234588 — Re: Self-hosting and the PDP-10 [was Re: Self-hosting and the 6502]

cross@spitfire.i.gajendra.net (Dan Cross) writes:

> In article <10qkrpq$qbu8$2@dont-email.me>,

> Peter Flass  <Peter@Iron-Spring.com> wrote:

>> I didn't know XKL was still in the business. I looked them up a while ago
>> and they seemed to be selling networking hardware.

Quite successfully, as it happens.  At the recent NANOG, Len Bosack was the
invited keynote speaker.

> They are and they do; the hardware (as I understand it) contains a custom
> ASIC for the networking side, and a control processor implemented on an FPGA
> that runs the modified TOPS-20 monitor that Rich described.  I was hoping
> there was sufficient product differentiation that they would (or could be
> persuaded to) release just the monitor component, but alas: that appears to
> be unlikely.

On power-on, the control processor checks for the presence of optical interfaces
in the box, and if it finds any it boots XKL's dxmOS monitor, a modern OS which
is specialized for network control.

If it does not find any optical interfaces, it will boot into TOPS-20 v7.1.

SDF.org has an XKL Darkstar sans optical interfaces on which one can request a
TOPS-20 account in order to experience the joys of yesterday.  (NB:  I am a
friend to SDF and the Interim Computer Museum, but am not otherwise associated
with them.)

-- 
Rich Alderson					  news@alderson.users.panix.com
      Audendum est, et veritas investiganda; quam etiamsi non assequamur,
	  omnino tamen proprius, quam nunc sumus, ad eam perveniemus.
									--Galen

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#234594 — Re: Self-hosting and the PDP-10 [was Re: Self-hosting and the 6502]

In article <mdd341d2mta.fsf@panix5.panix.com>,
Rich Alderson  <news@alderson.users.panix.com> wrote:
>cross@spitfire.i.gajendra.net (Dan Cross) writes:
>
>> In article <10qkrpq$qbu8$2@dont-email.me>,
>
>> Peter Flass  <Peter@Iron-Spring.com> wrote:
>
>>> I didn't know XKL was still in the business. I looked them up a while ago
>>> and they seemed to be selling networking hardware.
>
>Quite successfully, as it happens.  At the recent NANOG, Len Bosack was the
>invited keynote speaker.
>
>> They are and they do; the hardware (as I understand it) contains a custom
>> ASIC for the networking side, and a control processor implemented on an FPGA
>> that runs the modified TOPS-20 monitor that Rich described.  I was hoping
>> there was sufficient product differentiation that they would (or could be
>> persuaded to) release just the monitor component, but alas: that appears to
>> be unlikely.
>
>On power-on, the control processor checks for the presence of optical interfaces
>in the box, and if it finds any it boots XKL's dxmOS monitor, a modern OS which
>is specialized for network control.
>
>If it does not find any optical interfaces, it will boot into TOPS-20 v7.1.
>
>SDF.org has an XKL Darkstar sans optical interfaces on which one can request a
>TOPS-20 account in order to experience the joys of yesterday.  (NB:  I am a
>friend to SDF and the Interim Computer Museum, but am not otherwise associated
>with them.)

I highly recommend their service; it's pretty cool.  It's a bit
of a bummer that the Uppsala common Lisp system didn't survive
coming from the Panda distribution, but perhaps it wouldn't be
too hard to get it running (I haven't tried).

	- Dan C.

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#234572 — Re: Self-hosting and the PDP-10 [was Re: Self-hosting and the 6502]

In article <mdd341e86z6.fsf@panix5.panix.com>,
Rich Alderson  <news@alderson.users.panix.com> wrote:
>cross@spitfire.i.gajendra.net (Dan Cross) writes:
>
>> In article <mddv7eampsr.fsf_-_@panix5.panix.com>,
>> Rich Alderson  <news@alderson.users.panix.com> wrote:
>
>>> When XKL was developing their first product, code named "ToaD" = "10 on a desk",
>>> the primary work was done on a DECSYSTEM-2065 running TOPS-20 v6.1 (which I
>>> upgraded to v7.0 when I got there a couple of years later).
>
>>> Because the Toad was an extended clone of the KL-10 processor, featuring full
>>> 30 bit addressing, changes needed to be made to TOPS-20 to support the memory
>>> model in its full glory.
>
>> Rich, I think I've asked this before, but can't recall the answer.  Is that
>> monitor available publicly, outside of the XKL Darkstar or other hardware?
>> 30-bit addressing would be a nice extension over the monitor in the Panda
>> distribution.
>
>The XKL monitor is a commercial product, available only with the purchase of
>a compatible hardware system.

That's unfortunate.  I was hoping that XKL would see just that
component as a thing that they did not need to keep proprietary.

>The Panda distribution is of course intended for a KL-10 compatible processor
>(and was originally targeted at DEC hardware rather than simulator programs),
>so it of course does not have the expanded data structures to allow a full
>gigaword of memory.  Extending the monitor is left as an exercise for the reader.

Yet another project for our collectively copious spare time.
:-)

	- Dan C.

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#234576 — Re: Self-hosting and the PDP-10 [was Re: Self-hosting and the 6502]

On 4/2/26 03:58, Dan Cross wrote:
> In article <mdd341e86z6.fsf@panix5.panix.com>,
> Rich Alderson  <news@alderson.users.panix.com> wrote:
>> cross@spitfire.i.gajendra.net (Dan Cross) writes:
>>
>>> In article <mddv7eampsr.fsf_-_@panix5.panix.com>,
>>> Rich Alderson  <news@alderson.users.panix.com> wrote:
>>
>>>> When XKL was developing their first product, code named "ToaD" = "10 on a desk",
>>>> the primary work was done on a DECSYSTEM-2065 running TOPS-20 v6.1 (which I
>>>> upgraded to v7.0 when I got there a couple of years later).
>>
>>>> Because the Toad was an extended clone of the KL-10 processor, featuring full
>>>> 30 bit addressing, changes needed to be made to TOPS-20 to support the memory
>>>> model in its full glory.
>>
>>> Rich, I think I've asked this before, but can't recall the answer.  Is that
>>> monitor available publicly, outside of the XKL Darkstar or other hardware?
>>> 30-bit addressing would be a nice extension over the monitor in the Panda
>>> distribution.
>>
>> The XKL monitor is a commercial product, available only with the purchase of
>> a compatible hardware system.
> 
> That's unfortunate.  I was hoping that XKL would see just that
> component as a thing that they did not need to keep proprietary.

It's unlikely that anyone would steal it, given the current dearth of 
PDP-10 hardware.
> 
>> The Panda distribution is of course intended for a KL-10 compatible processor
>> (and was originally targeted at DEC hardware rather than simulator programs),
>> so it of course does not have the expanded data structures to allow a full
>> gigaword of memory.  Extending the monitor is left as an exercise for the reader.
> 
> Yet another project for our collectively copious spare time.

Not that I would work on it, but are at least the architecture specs for 
the TOAD available? Did XKL patent their ideas?

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#234585 — Re: Self-hosting and the PDP-10 [was Re: Self-hosting and the 6502]

In article <10qlumn$15ji5$2@dont-email.me>,
Peter Flass  <Peter@Iron-Spring.com> wrote:
>On 4/2/26 03:58, Dan Cross wrote:
>> In article <mdd341e86z6.fsf@panix5.panix.com>,
>> Rich Alderson  <news@alderson.users.panix.com> wrote:
>>> cross@spitfire.i.gajendra.net (Dan Cross) writes:
>>>
>>>> In article <mddv7eampsr.fsf_-_@panix5.panix.com>,
>>>> Rich Alderson  <news@alderson.users.panix.com> wrote:
>>>
>>>>> When XKL was developing their first product, code named "ToaD" = "10 on a desk",
>>>>> the primary work was done on a DECSYSTEM-2065 running TOPS-20 v6.1 (which I
>>>>> upgraded to v7.0 when I got there a couple of years later).
>>>
>>>>> Because the Toad was an extended clone of the KL-10 processor, featuring full
>>>>> 30 bit addressing, changes needed to be made to TOPS-20 to support the memory
>>>>> model in its full glory.
>>>
>>>> Rich, I think I've asked this before, but can't recall the answer.  Is that
>>>> monitor available publicly, outside of the XKL Darkstar or other hardware?
>>>> 30-bit addressing would be a nice extension over the monitor in the Panda
>>>> distribution.
>>>
>>> The XKL monitor is a commercial product, available only with the purchase of
>>> a compatible hardware system.
>> 
>> That's unfortunate.  I was hoping that XKL would see just that
>> component as a thing that they did not need to keep proprietary.
>
>It's unlikely that anyone would steal it, given the current dearth of 
>PDP-10 hardware.

It's unlikely that the monitor itself is of much commercial
interest.  I guess the questions are whether any of their
networking specific IP is wrapped up in the monitor, and whether
it's worth their while to do the work of dropping their monitor
sources onto the net somewhere.  And of course whether they'd
want to do it at all; kinda sounds like maybe they don't (or are
just too focused on other, higher priority things to be
bothered.  I can sympathize with that).

>>> The Panda distribution is of course intended for a KL-10 compatible processor
>>> (and was originally targeted at DEC hardware rather than simulator programs),
>>> so it of course does not have the expanded data structures to allow a full
>>> gigaword of memory.  Extending the monitor is left as an exercise for the reader.
>> 
>> Yet another project for our collectively copious spare time.
>
>Not that I would work on it, but are at least the architecture specs for 
>the TOAD available? Did XKL patent their ideas?

Good question.  I don't know if they could reasonably patent
that, but IANAL.

	- Dan C.

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#234445 — Re: virtualization, Self-hosting and the 6502

According to Lev <thresh3@fastmail.com>:
>Lawrence wrote:
>> IBM invented virtualization, not as a clever solution to an 
>> important problem, but as a fudge.

Not really.  IBM developed TSS/360 to be their flagship time-sharing system
which collapsed of its own weight.  It worked, I used it, but it struggled to
handle 20 users on a 360/67.  It suffered from being a very large design
implemented by a very large staff.

CP/67 was originally an experiment at IBM Research to provide a better
development environment for operating systems than a signup sheet to let one
person at a time use the physical machine. It was written by a small group of
skilled programmers who got really good performance out of the same hardware. At
the same time they wrote the single user CMS monitor which, unlike TSS, emulated
enough of OS/360 to run OS compilers, so between the performance and the OS
compatibility, CP won and turned into VM/370. It's also still used for the
original purpose, runing production and development systems at the same time on
the same hardware.  It's a standard feature of IBM mainframes, under the name
LPAR for Logical Partitions.

Sort of ironically, after TSS/360 was abandoned as a product, it stayed alive
with a skeleton staff as a specialty product, beause the Bell System was using
it as a development platform for its phone switches. The skeleton staff went
back and redid a lot of the code and by the time TSS finally died, it worked
pretty well.

-- 
Regards,
John Levine, johnl@taugh.com, Primary Perpetrator of "The Internet for Dummies",
Please consider the environment before reading this e-mail. https://jl.ly

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#234447

On 30 Mar 2026, Lawrence D´Oliveiro wrote
(in article <10qd499$26t67$3@dont-email.me>):

> On Mon, 30 Mar 2026 01:16:44 -0000 (UTC), Lev wrote:
>
> > I know about VM/370 and the whole IBM lineage, but that's mainframe
> > territory.
>
> IBM invented virtualization, not as a clever solution to an important
> problem, but as a fudge. ...
>
> It was an expensive and unwieldy way to implement multiuser support.

You can say this for Lawrence: he is not as wrong about everything as Lev.

-- 
Bill Findlay

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#234458

On Mon, 30 Mar 2026 17:59:00 +0100, Bill Findlay wrote:

> On 30 Mar 2026, Lawrence D´Oliveiro wrote
> (in article <10qd499$26t67$3@dont-email.me>):
>
>> On Mon, 30 Mar 2026 01:16:44 -0000 (UTC), Lev wrote:
>>
>> > I know about VM/370 and the whole IBM lineage, but that's mainframe
>> > territory.
>>
>> IBM invented virtualization, not as a clever solution to an important
>> problem, but as a fudge. ...
>>
>> It was an expensive and unwieldy way to implement multiuser support.
>
> You can say this for Lawrence: he is not as wrong about everything as Lev.

What is it? Are people going by folklore? Listening to IBM marketing
salespeople? Faulty personal memories? Not looking at actual records
from the time?

Answers on a postcard, please ...

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#234436

In article <10qcitr$22aag$1@dont-email.me>, Lev  <thresh3@fastmail.com> wrote:
>Came across an article recently about running a 6502
>emulator on a 6502 - not as a joke but as a practical
>exercise. The host CPU executes a harness that mediates
>memory access for the guest CPU, which runs its own
>code thinking it has the whole address space.
>
>What struck me wasn't the technical trick but the
>historical question. How early did people start running
>machines inside machines? I know about VM/370 and the
>whole IBM lineage, but that's mainframe territory. Was
>anyone doing this on micros in the late 70s/early 80s?
>Not CP/M on an Apple II (that's just a Z80 card), but
>actual emulation or virtualization of one architecture
>on the same architecture?

It depends on what you mean by, "running machines inside
machines".  There are two primary methods: emulation, in which
one machine completely emulates another in software; people have
been doing that since, probably, the 50s; perhaps earlier.

Then there is virtualization, in which the "virtual mchine" is
primarily running directly on the underlying hardware, in which
case AFAIK IBM was the first with CP/40, which evolved into
VM/370.

Melinda Varian has written a wonderful and extensive history of
VM: https://www.leeandmelindavarian.com/Melinda/25paper.pdf
She points to L.W.Comeau's paper on the history of CP/40 and
VM/370:
https://www.leeandmelindavarian.com/Melinda/JimMarch/CP40_The_Origin_of_VM370.pdf

(The bottom line is that IBM fully expected to be the target for
Multics development and was shocked when GE was selected for
project MAC instead.  CP/40 was a bit of a skunkworks project
for the team in Cambridge, MA, that had been stood up to support
MIT in particular as a customer.)

>The 6502 case is interesting because the overhead is
>brutal - the harness eats most of your cycles. On a
>mainframe you could hide the cost. On a 1MHz micro you
>really feel it. Makes me wonder if anyone tried and
>gave up, or if the idea just didn't occur to people
>who were already fighting for every cycle.

I don't know how one could "hide the cost" on a mainframe any
more than on a microcomputer.  I'm not even sure what that would
mean.  And besides, the IBM 360/40 that VM originated on was not
exactly a screamer by modern standards.  The IBM 360/30 had a
clock speed around 1MHz, for example; the /40 wasn't much
faster.

Anyway, the idea of virtualization was well-known by the dawn of
the microprocessor era.  I imagine that much of the reason it
wasn't implemented more widely was lack of a compelling use
case: microprocessor OSes were not timesharing systems and were
mostly targeted towards a market that wasn't interested in
multitasking yet.  Certainly, the hardware surrounding the main
CPU was pretty limited (mainframes were designed for throughput,
micros not so much), but timesharing drove virtualization, and
that was driven by cost considerations: microcomputers were
cheap enough that it just wasn't much of a factor.

Also, in the 1970s, Popek and Goldberg sat down to study
virtualization formally, and articulated a set of requirements
for machines to be virtualizable; the gist of it is that
privileged state, and evidence of privileged state (for example,
the current state of the CPU with respect to whether it's acting
in supervisor mode or user mode) had to be "hidden".  Many early
microprocessors didn't have a concept of privileged state
separate from normal operating state, at all.  Thus, they could
not be virtualized in the classical sense because they simply
didn't meet the requirements.  In particular, x86 violated the
P&G virt requirements in a number of ways, and was considered
un-virtualizable.

This changed in the 1990s, when research into paravirtualization
showed it to be viable on x86 (Xen), and when the Disco research
project at Stanford showed that the idea was tractable on
commidity hardware: Disco targeted MIPS on SGI machines, but the
team that built it went on to found VMWare, focused on
virtualizing x86; they observed that dynamic binary translation
could be used to paper over the non-virtualizable parts of the
architecture, effectively employing a limited amount of
emulation to force x86 systems to use a subset of x86 that could
be classically virtualized.  Intel and AMD subsequently came out
with extensions to aid this, and to make it fast.
https://dl.acm.org/doi/epdf/10.1145/2382553.2382554

>Related: the Gigatron runs a Harvard-architecture RISC
>CPU built from 7400-series TTL that manages to emulate
>a vCPU with a different instruction set for user
>programs. That's closer to what VM/370 was doing than
>most micro-era attempts. The abstraction layer is the
>whole point, not the inefficiency.

No, that's not what VM/370 was doing.  VM/370 exposes a virtual
370 machine that's a pretty faithful facsimile of the underlying
hardware, though it is not total:  there _are_ a few things that
are paravirtualized.  But a normal "add" instruction on a VM/370
virtual machine is just the ordinary 360/370 "A" instruction.

Interesting that this came up in the context of virtualization;
the 360/40 system that CP/40 was written for included a 1401
emulation mode, which _does_ emulate a different instruction
set.

	- Dan C.

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#234440

On 3/30/26 07:16, Dan Cross wrote:
[snip]
> 
> It depends on what you mean by, "running machines inside
> machines".  There are two primary methods: emulation, in which
> one machine completely emulates another in software; people have
> been doing that since, probably, the 50s; perhaps earlier.
> 
> Then there is virtualization, in which the "virtual mchine" is
> primarily running directly on the underlying hardware, in which
> case AFAIK IBM was the first with CP/40, which evolved into
> VM/370.
> 

The difference here is clear. My question is, what's the difference 
between emulation and simulation? Is there a difference, even if only in 
connotation.  I'm never quite clear on whether to call something an 
emulator or a simulator.

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#234446 — Re: emulation, virtualization, Self-hosting and the 6502

According to Peter Flass  <Peter@Iron-Spring.com>:
>The difference here is clear. My question is, what's the difference 
>between emulation and simulation? Is there a difference, even if only in 
>connotation.  I'm never quite clear on whether to call something an 
>emulator or a simulator.

The usual rule of thumb is that emulation involves hardware or microcode support,
simulation is just software.

Virtualization is something else, where the architecture of the internal system
is the same as the external system so you can run the same operating system in
a virtual machine you can on the hardware, give or take very small tweaks. 

As far as I can tell, it was an accident that the architcture of S/360 made it
possible to build a virtual machine system.  A program in user mode ("problem
state") cannot see or change any of the system state, and all attempts to do
so trap so they can be simulated.  The only exception I can think of is the
realtime clock, which they fudged.  It also helped that the I/O was all done
by channels so there were relatively few I/O events to simulate, not like
a PDP-10 which took an interrupt on each character from a TTY or each data
word from a DECtape.

I don't think you could have built a virtual machine OS on a PDP-10, because there
was too much of the system state visible to user programs.

-- 
Regards,
John Levine, johnl@taugh.com, Primary Perpetrator of "The Internet for Dummies",
Please consider the environment before reading this e-mail. https://jl.ly

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#234451 — Re: emulation, virtualization, Self-hosting and the 6502

In article <10qe90l$kv9$2@gal.iecc.com>, John Levine  <johnl@taugh.com> wrote:
>According to Peter Flass  <Peter@Iron-Spring.com>:
>>The difference here is clear. My question is, what's the difference 
>>between emulation and simulation? Is there a difference, even if only in 
>>connotation.  I'm never quite clear on whether to call something an 
>>emulator or a simulator.
>
>The usual rule of thumb is that emulation involves hardware or microcode
>support,
>simulation is just software.
>
>Virtualization is something else, where the architecture of the internal system
>is the same as the external system so you can run the same operating system in
>a virtual machine you can on the hardware, give or take very small tweaks. 
>

I would say that's not quite complete, as you had the 386 being able to
virtualize the 8086, but not itself.
-- 
columbiaclosings.com
What's not in Columbia anymore..

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