Re: MISC-d Digest V96 #12

[gut@xxxxxxxxxxxxxxxxx (alex lasky)]

MISC-d-request@pisa.rockefeller.edu writes:
> > From: Jaap van Ganswijk <ganswijk@xs4all.nl>
> > 
> > Since you're talking about 'stack based architectures': Does anybody
> > know what happened to the Hobbit, which is in my opinion the best
> > chip architecture ever. (From the viewpoint of a compiler writer. ;-)
> 
> I used to work for Eo, the only people who ever used the Hobbit AFAIK.
> AT&T Microelectronics decided to stop producing the chip when it
> became clear that nobody other than Eo was going to use it, and the Eo
> wasn't selling.
> 
> Since then, advances in register based machines and the compilers for
> them have made the CRISP architecture obsolete as a platform for
> running C: after all, the only real reason for the Hobbit's design was
> the (IMHO bogus) semantics of C.

The 9 March issue of New Scientist has an article on strategies to make
chips work faster. After blaming some inexplicable crashes on increasing
compiler complexity due to RISC strategies [but no mention of MS Windows],
the article says:

"In an attempt to eliminate these problems, Simon Wiseman and Hugh Field-
Richards at the Defence Research Agency in Malvern
have developed the High Order Language Instruction Set Computer
(HOLISTIC). This approach does not shift complexity beetween software and the
instruction set but attempts to remove it altogether. To do this, Wiseman
 and Field-RIchrads have tried to reduce the "semantic gap" between high-level
languages that human progarmmers write and the  instructions to which computers
respond.

"The C programming language makes use of a concept called a "stack" in which
programs written in C keep a record of the variables used and the memory
addresses in which they are stored. But the stack is an abstraction: it has no
meaning outside the software world. At the hardware level, variables and
addresses are stored not in stacks but in memory registers on the processor chip
and in the main memory.
One of the most complex and time-consuming tasks that a compiler carries out
is juggling variables between registers and the main memory.

"The aim of the HOLISTIC approach is to reorganise the chip's memory so it
looks like a stack to the programming language, while the processor sees it as
a series of registers. "The trick is to make the two views happen at the same
time", says Wiseman. "If it works then we would not have Macs and PC's
crashing randomly". Simplifying the computer is also likely to make life easier
for programmers.

"[...] We got as far as the paper design for the processor and a rough idea
of a compiler when the funding dried up". In the meantime he and Richrads
have  applied for a patent on the technology."


Alex Lasky            * "Clubland & dubland will bop till they drop, then
gut@elec.apana.org.au * discuss postmodernism & the punk ethos over pools of
Sydney, Australia     * 70%-proof vomit on the toilet floor" - Ian Mcdonald