Date : Tue, 23 Aug 2011 12:06:05 +0100
From : famrowland@... (famrowland)
Subject: Tube ROM
I'm not sure that it was performance that was the Achilles heel of the whole
co-pro concept, but the video limitations. Sure, co-processors were produced
and the Tube came in useful sometimes (one thinks of early ARM programming),
but with the exception perhaps of the Master 512, it was mostly pretty niche
and far from main stream. The real limitation was the video. I would have
killed for a 4-colour Mode 0 back in the day (80?32?4), but you were never
going to get that on any machine hosted on a beeb. If Acorn wanted to make
things modular so you could upgrade, they should have put the video on a
separate card like PCs did, not the processor. Acorn nearly got video right
-- the VDU calls to change colour left three bytes free to enable later RGB
-- and then messed it up by using the top bit of the first parameter to set
the background colour, which made VGA impossible. Hence all the daft
limitations and messing around with TINT in Basic V.
So ultimately, it wasn't the CPU that was the bottleneck but the I/O, and
they targeted the wrong thing.
Discuss ;)
Andrew
-----Original Message-----
From: bbc-micro-bounces+famrowland=freeuk.com@...
[mailto:bbc-micro-bounces+famrowland=freeuk.com@...] On
Behalf Of Jules Richardson
Sent: 21 August 2011 17:16
To: bbc-micro@...
Subject: Re: [BBC-Micro] Tube ROM
Rob wrote:
> On 18 August 2011 15:46, Rick Murray <rick@...> wrote:
>> Ah, but the logic here is that the HiBASIC simply *will* *not* work
>> if the co-processor isn't connected. It isn't like the Master's
>> auto-relocate one, it just... plain won't work.
>
> I think the theory was that the co-processor became "the computer" and
> the BBC Micro was just a means by which you interacted with it.
Yes, the beeb just became the "I/O processor" as Acorn put it. A very nice
idea when the beeb was developed, but by the time people were trying to
exploit it, performance was just way too slow for what users needed.
cheers
Jules