[BBC-Micro] Subject: Re: 'BASIC 512K'
jules.richardson99 at gmail.com
Sun Feb 14 17:18:24 GMT 2010
jgh at mdfs.net wrote:
> Rick Murray wrote:
>> I wonder if the co-pro was a side effect of Acorn looking for a
>> worthwhile RISC chip for their new range of processors?
> It was. Acorn were looking for something to step from 8-bit 6502s
> to a suitable 32-bit CPU. They approached Intel to see if they
> could license the 80x86 core, but Intel were only interested in
> selling physical chips.
What puzzles me is why they didn't go m68k - everyone else was around that
time. Did they go out of their way to try and be different, or was there some
other reason for rejecting it? (I'd have to check to see if Torch's Neptune
copro was around by then - maybe it was, and so they considered the m68k
market to be already cornered)
> The 32016 gave Acorn the experience that showed that short, fast
> instructions and fast interupt response was what was important.
> Some 32016 instructions are 12 bytes long, BBC BASIC on an 8MHz
> 32016 barely manages to perform as well as BBC BASIC on a 2MHz
Yes. Some of the info I have on Xenix port to the 32016 suggests that they
were having *major* problems with interrupt response (and in part due to the
slow transfers across the TUBE) - reading between the lines it was clear by
then that a BBC micro / copro setup just wouldn't cut it any more, no matter
how good the copro was.
Funny thing is, I did spot some later documentation which suggests that they
(Acorn) were thinking about ditching ARM when they were thinking more
seriously about getting into the UNIX market, even though ARM had proved
itself a capable-enough CPU by that point. (I also unearthed some stuff which
hints at a Svr4-based UNIX release on Acorn hardware, circa 1993 or so - that
would have been into A4000/A5000 territory, I think)
> The beauty of the Tube system was that it takes a very small bit of
> hardware and firmware to throw together a system that lets you
> experiment with a new CPU without having to build an entire system
> - the system is already there in the host processor. Typically, you
> only need about 1K of client code, a Tube ULA and a couple of glue
It was certainly nice that Acorn had the foresight to make it a built-in part
of the firmware. I don't think the hardware side of it was particularly
unique, but the software bit was (to a great extent).
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