Re: Hobbit again

[Jaap van Ganswijk <ganswijk@xxxxxxxxx>]

At 10:44 AM 3/18/96 GMT, you wrote:
>> Date: Mon, 18 Mar 1996 01:51:54 +0100
>> From: Jaap van Ganswijk <ganswijk@xs4all.nl>
>> The Hobbit has (almost) no registers and uses a cache on the stack memory
>> instead. Compared to Forth engines and other pure stack machines it has a
>> very orthogonal instruction set however and can manipulate not only the
top of
>> the stack but also local variables higher up on the stack. Which helps
>> compiled C/Pascal/... a lot.
>> Just see the upper positions on the stack as registers in cache...
>> .
>> People try to tell me, that this concept can't be efficient, but I don't see
>> why...
>
>It's less efficient because it makes the datapath in the CPU more
>complicated.  For example, superscalar execution is inhibited because
>it's possible that a stack element may be rewritten by a memory
>reference after it has been issued as a operand to an execution unit.
>The only way to solve this problem is to heave a complex interlock
>within the CPU.

We must learn to live with the fact, that CPU's are complicated
if we want them to do complicated tasks (quickly).

>With CPUs, simpler is better.  The only advantage of Hobbit is that it
>allows one to take the address of a stack element: that's a language
>misfeature.

I beg to differ:
The number of spaces in a computer should be as few as possible,
with a clear optimum of there being only one space.
Obviously, this space would be the memory space.
Other spaces like the register space, the stack space and the
IO space should be part of this space.
Since the memory space should allow taking the address of an
element, any of the other spaces should also allow this...

I realize, that some would like to improve the world by
forbidding 99% of the languages that the world currently uses,
but in day-to-day life, if your processor can't handle these
languages efficiently, you won't sell your processor,
since the world isn't prepared to (and can't) rewrite all
the programs it has written so far...

I'll seperately post some other problems to the list that
all suggest: Hobbit!

Groeten,
Jaap

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