Date   : Mon, 05 Apr 2010 11:33:23 -0500
From   : jules.richardson99@... (Jules Richardson)
Subject: "open" beeb bits...

Mark Usher wrote:
>  
>> Problem is, exactly what is involved in recreating something like the
>> video ULA? Not only that, but recreating it accurately enough that any
>> drop-in replacement functions just like the original. Spare a moment
>> for how complicated this process is!
> 
> and, if the parts you use to do it are available in 50 years time...

Yep - the way I see it, the documentation for how it works and what it needs 
to do stays the same, but the actual implementation depends on what silicon is 
available at any moment in time (and it doesn't hurt to have several 
alternatives lined up anyway). Whatever the solution, a simple adapter/carrier 
board should be all that's needed to actually install it.

I'm indifferent over whether any solutions should have any 'enhanced' 
features, but I would like to ensure that a "100% compatible" solution was 
always available for any "drop in replacements" of beeb bits.

> As it
> doesn't seem to be a requirement yet (there are still plenty of donors etc)

Hmm. Last I looked, it was extremely hard to get hold of a TUBE ULA without 
tearing into an existing copro / Springboard / whatever - they just didn't 
really exist any more except as pulls from existing kit (which I'd much rather 
see fixed).

Same goes for video ULAs - I'd rather see systems fixed than sacrificed.

Things like the CPU and VIAs (and probably FDC) are less of a problem at this 
stage - although probably not as true in 10 or 20 years.

With my preservation hat on, I don't really believe in junking one donor 
system to get another one running!

> it doesn't seem particularly worthwhile in investing significant time doing
> so, unless of course it is a project under the "because I can" banner.

Well, what other reason is there for any of the stuff that we do? :-)

> What
> is valuable is documenting the knowledge / operation of the device before
> that is lost. Of course, an excellent method of documenting something is to
> try and build it... back to start of paragraph :-)

I think you mean "GOTO 10" :-)

I've got plenty of online "permanent" space that I could host things at - but 
I'm rather lacking in the necessary technical knowledge (other than having 
things like what's in the user manuals*, Hugo's TUBE notes etc.).

* On the TUBE front, I think I have some useful Torch docs, too - even though 
they didn't use Acorn's TUBE ULA, I think somewhere they did scribble down a 
reasonable explanation of what it all does. Not sure if I have that docs 
scanned and here with me in the US, though.

cheers

Jules