Date   : Thu, 20 Apr 2006 16:47:24 +0100
From   : Jules Richardson <julesrichardsonuk@...>
Subject: Re: 8 bitter list (Was: Re: Keyboard)

Mike Tomlinson wrote:
> In article <44395FA3.9040001@...>, Fragula
> <fragula@...> writes
> 
>> BTW what you (all of you) think about the idea of sticking a dongle with
>> some fast buffers on the Tube, for the purpose connecting half a dozen
>> or so (dissimilar) cheesewedge 2nd processors on it, powered one at a
>> time enforced from a selection switch? The 2nd processor boxes captive
>> cables each joined with IDC sockets onto a single longish (1.5M or so)
>> IDC cable, i.e. simultaneously connected, but only one powered.
>> (possibly with some passive termination at the end...)
> 
> Uh, I think you'll be very lucky if it works at all, never mind works
> reliably over 1.5m+ with that sort of loading on it.

Hmm, gut feeling is that it wouldn't work - but then OTOH SCSI works quite 
happily with TTL over that sort of cable length, so maybe if the buffering's 
done right (and at the BBC end as well as each device) it could work.

Don't all TUBE deices expect to be the only thing on the bus and so bias the 
data lines accordingly though? Not sure - not enough coffee yet this morning!

I really think Acorn missed a trick with this aspect of the beeb design 
though, in not realising that people might want more than one device on the 
TUBE (even if only one was active without a system reset)

cheers

Jules