[Simh] RSX-20F

[Timothe Litt]

On 19-Mar-15 18:43, Johnny Billquist wrote:
>
> All true. Except I don't think VMS actually do relocation at load
> time. The VAX instruction set was capable enough that pretty much all
> code you ever wrote was already PIC. The only things to resolve were
> external symbols, but I don't think VMS allowed shareable images to
> refer to external, unresolved symbols to start with. But I might be
> wrong on that.
>
You are.  The image activator dealt with G^ symbol fixups.  One tried to
avoid them, as they caused imgact to do extra work, and the instructions
that needed to be fixed-up made their pages non-sharable.  You can write
PIC code, on VAX, but don't have to.  But that's another diversion, and
I have other things to do.
>
>
> And yes, -20F looks truly like a weird hybrid, with even the
> documentation not correct.
>
The documentation is correct, as far as it goes.  It's just not
complete.  Any doc has some errors.  And this was reverse-engineered.
Be grateful that some of us fought for funding to get the internal notes
and training materials published.

> Probably.  But unless you also have 11D code, don't be too sure.  11M
>> practiced code reuse before it was popular.  M may have started with D's
>> BOOT.
>
> Nope. The comments in the BOOT sources even says it is 11M.
>
That doesn't contradict my point.  Its origin may well have been 11D,
before 11M adopted it.
>> his was the basis of the 20F drivers.
>
> Loadable device drivers have been around for a long, long time in 11M.
> But, unlike 11D, device drivers in 11M were never tasks.
I've been around longer.  When I first used 11M, they had to be sysgened
into the exec.  It was big news when they became (optionally) loadable. 
And somewhat of a pain to upgrade, though avoiding the full exec TKB was
helpful when developing.

> And the drivers in -20F do appear to be like tasks, and they even
> define the RSX11D symbol, so they definitely are in the 11D vein.
>    

As I said, keep looking and you'll keep validating what I wrote.  This
started when I said the drivers came from 11D, and you disbelieved me...

As far as I'm concerned, this conversation is over.


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