Re: SMP support for 680[34]0 ?

Le ven. 29 déc. 2023 à 19:43, Izumi Tsutsui <[email protected]> a écrit :
> Actually LUNA-II seems to have a socket for the optional
> (secondary?) processor around 68040 on its motherboard,
>  https://twitter.com/tsutsuii/status/356427858018701312
> but I have seen no article about such actual hardware options.

Oh, nice setup. I'm guessing no schematics or any other information on
what signals are connected to the socket(s)?
One of my (many) questions is which signals can safely be bussed, and
which needs to be point-to-point between the CPU and the arbiter (or
the rest of the hardware, such as interrupts).

> Anyway, if there is ~no real hardware, I'm afraid very
> few people (developers) are interested in SMP support
> (that is too complex).

Assuming hardware could be made to work (working atomic TAS/CAS/CAS2,
coherency maintained, probably by forcing everything to write-through
at first to simplify the arbiter), how complex?
I would think a lot of the support is 'common', and a port would only
need some machine-specific primitives for synchronization, etc., but I
haven't really looked so I could be way off base...
Is there some document/reference explaining what's needed to add SMP
to a port? Just so I know how crazy this idea really is :-)

Thanks & cordially,

-- 
Romain Dolbeau