Date   : Tue, 26 Jul 2005 15:27:12 +0000
From   : Jules Richardson <julesrichardsonuk@...>
Subject: Re: ARM copros, speech cartridges, real timeclocks, etc

On Tue, 2005-07-26 at 13:54 +0200, Johan Heuseveldt wrote:
>   Technical: Indeed this is a bus: all connector pins are connected to
>               each other, except the ULA Select line, which comes from,
>               lets say, an (74LS)138, allowing 8 2ndProc's. A latch (as
>               the physical paging register) and address decoding completes
>               the hardware, perhaps added with an extra power input.

So what's the issue with bus loading on the Tube? Does it just not have
any buffers at all or something (which could be added) - or is there
more to it than that?

> A note to Sprow: Would this be of interest of you, to create such
>                   a 'Tube Selector' board, and make it part of your
>                   current list of hardware projects?
>                  More sophisticated approaches are possible. like
>                   prioriterized interrupts ('like' on the SCSI bus),
>                   so some brain storming on the list seems valid. :-)

I thought there were no interrupts at present and it was just done by
the beeb polling the Tube every so often - or did I misread that? Adding
a prioritized interrupt system to something that has no interrupt system
at all might get messy?

Now if I could get a Z80, 6502, 32016, 80186, 80286 (from the ABC310),
ARM, Torch Z80, Torch 68000 and Torch Graduate all on the same beeb it'd
be something of a monster! :-)  (I'd be inclined to make the Dragon 64
copro then too)

Of course there'd probably be all sorts of horrible software conflicts
having support for that lot in the same beeb at once...

cheers

Jules