Re: fractional PCs

On 02/05/2025 18:22, EricP wrote:

moi wrote:

On 02/05/2025 16:18, EricP wrote:
>

And a paper on IBM Millicode which is kind of like Alpha PAL code
and may be similar to Robert's mega-ops.
>
The What and Why of System z Millicode 2012
https://share.confex.com/share/119/webprogram/Handout/Session11773/The%20What%20and%20Why%20of%20System%20z%20Millicode%20-%20%2311773.pdf

>
Thanks for that reference.
>
I struggle to see how "miilicode" differs in essentials from
the "extracode" implementation of complex orders on the
Ferranti Orion & Atlas, or the ICT 1900 Series, of 60 years ago.

  From what I can find, they sound somewhat similar.
Extracode is normal ISA instructions stored in a
separate memory accessible in a special mode.

Separate memory on on Atlas.

Both PAL and Milli code also use the ISA format instructions
stored in separate memory and a special mode. However they also
disable interrupts and give access to special hardware registers.

As do Orion and 1900 Series extracode.
--
Bill F.