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Re: Almost Ready to Repeat the Cycle

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On 22/10/2026 05:52, John Levine wrote:
> According to BGB  <cr88192@gmail.com>:
>>>> So if I couldn't figure out a simple way of trivially modifying my
>>>> ISA to make it closer to isomorphic with the target architecture, I
>>>> could just literally emulate, using actual 360 instructions!
> 
>> At some level of feature cost, it may become preferable to emulate a
>> feature, or maybe the whole ISA, rather than invest the cost in native
>> hardware support. Where exactly this line is, depends some on the use-case.
>>
>> For a more complex ISA with more complex decoding, it may be preferable
>> simply to emulate it.
> 
> That sounds a lot like IBM's Millicode they use in their mainframes.  The hardware
> implements the simple instructions, complex ones run millicode which uses those
> instructions plus a few others to access internal registers.
> 

That was known as "extracode" on the Ferranti Orion (~1960)
and the Ferranti Atlas (~1964).

It was also the means of establishing order code compatibility
across a range of m/cs - the 1965 ICT/ICL 1900 Series - having
a wide span of performance and varied h/w bases.
The smallest 1900s did * and / in extracode, e.g.

I/O handling and multithreading were extracode throughout the range.

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Almost Ready to Repeat the Cycle quadibloc@invalid.com (John Savard) - 2026-10-18 18:39 +0000
  Re: Almost Ready to Repeat the Cycle quadibloc@invalid.com (John Savard) - 2026-10-18 18:47 +0000
    Re: Almost Ready to Repeat the Cycle quadibloc@invalid.com (John Savard) - 2026-10-18 22:00 +0000
      Re: Almost Ready to Repeat the Cycle quadibloc@invalid.com (John Savard) - 2026-10-20 17:12 +0000
  Re: Almost Ready to Repeat the Cycle jgd@cix.co.uk (John Dallman) - 2026-10-20 20:21 +0100
    Re: Almost Ready to Repeat the Cycle BGB <cr88192@gmail.com> - 2026-10-21 15:28 -0500
      Re: Almost Ready to Repeat the Cycle John Levine <johnl@taugh.com> - 2026-10-22 04:52 +0000
        Re: Almost Ready to Repeat the Cycle Bill Findlay <findlaybill@blueyonder.co.uk> - 2026-10-22 23:42 +0100
      Re: Almost Ready to Repeat the Cycle MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-10-22 16:10 +0000
        Re: Almost Ready to Repeat the Cycle anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-10-22 16:47 +0000
          Re: Almost Ready to Repeat the Cycle BGB <cr88192@gmail.com> - 2026-10-22 20:23 -0500
            Binary translation (was: Almost Ready to Repeat the Cycle) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-10-23 07:55 +0000
              Re: Binary translation BGB <cr88192@gmail.com> - 2026-10-23 03:50 -0500
                Re: Binary translation anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-10-23 16:21 +0000
                Re: Binary translation jgd@cix.co.uk (John Dallman) - 2026-10-23 23:51 +0100
              Re: Binary translation antispam@fricas.org (Waldek Hebisch) - 2026-10-25 00:10 +0000
                Re: Binary translation aph@littlepinkcloud.invalid - 2026-10-25 19:49 +0000
          Re: Almost Ready to Repeat the Cycle Stefan Monnier <monnier@iro.umontreal.ca> - 2026-10-22 15:45 -0400
            Binary translation (was: Almost Ready to Repeat the Cycle) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-10-23 08:13 +0000
              Re: Binary translation (was: Almost Ready to Repeat the Cycle) Michael S <already5chosen@yahoo.com> - 2026-10-23 12:24 +0300
                Re: Binary translation (was: Almost Ready to Repeat the Cycle) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-10-23 16:41 +0000
              Re: Binary translation (was: Almost Ready to Repeat the Cycle) jgd@cix.co.uk (John Dallman) - 2026-10-23 23:51 +0100
            Re: Almost Ready to Repeat the Cycle quadibloc@invalid.com (John Savard) - 2026-10-23 14:53 +0000
              Re: Almost Ready to Repeat the Cycle quadibloc@invalid.com (John Savard) - 2026-10-23 15:08 +0000
          Re: Almost Ready to Repeat the Cycle jgd@cix.co.uk (John Dallman) - 2026-10-23 17:22 +0100
            Re: Almost Ready to Repeat the Cycle anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-10-23 21:20 +0000

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