Re: CPUs and Forth
In message <394D1999.DADFAC4@ultratechnology.com>, Jeff Fox
<fox@ultratechnology.com> writes
[snipped]
>I actually think that the lack of confidence in Forth has
>been the major problem with Forth chips. The RTX was a
>killer Forth chip but Harris put their major push behind
>C and it seems that C programmers often have a great deal
>of hostility toward Forth. I recall when I first heard
>Mitch Bradley do a presentation on Open Boot he never
>once mentioned the word Forth. He was asked why he would
>talk about a version for Forth for an hour and a half
>without ever using the word Forth.
[...]
>An excellent example is the ShBoom. Chuck did ShBoom in 1988,
>word addressing, etc. After the design ended up at Patriot
>they had a team of engineers who spend ten years making the
>chip ten times bigger so that it could efficiently support
>C and Java. Converting it from a Forth chip to a C and Java
>chip was a big project.
[...]
>Meanwhile at the same time Chuck continued to explore the
>ideas from ShBoom in the MISC chips. He was interested in
>going the VLSI route because the price (manufacture) and
>performance ratio is 100 to 1000 times better than with
>a generic PGA approach.
>
>The changes to ShBoom made it look good to a C or Java programmer.
>However if you ask the design engineers who had more experience with
>Forth they may tell you that those same changes really messed
>up the chip for Forth. They make all sorts of things that were
>simple in Forth before very complicated. One of the engineers
>refered to these changes as "brain damage." I think to understand
>why this is so requires understanding the chip before and
>after the changes and from a Forth software point of view. As
>I say the changes look good and minimal to a C or Java programmer
>but to a Forth programmer (with a perspective similar to Chucks) it
>is a completely different chip. It is much more expensive, much more
>complicated and and much more difficult to use for Forth. A Forth
>programmer with a perspective more like C (or ANS) might see the
>changes as useful to their idea of Forth in C or whatever.
Could you expand on this, Jeff? I use the PSC1000 and I'm very pleased
with its Forth performance. I needed something which was better than
the (now obsolete) RTX2001 which I'd been using for years and the
Patriot chip seems to fit the bill. I don't know of any (currently)
commercially available alternative. At $10 it's still inexpensive for
my applications.
I wrote a workable Forth cross-compiler running under Win32Forth in a
week and found the whole thing quite straightforward. The only
complicated parts of the chip are the various memory timing registers
which take (me) a lot of head scratching to work out.
I don't have a C (or ANS) perspective - what sort of changes (other than
marketing) were made to the original ShBoom design?
Cheers and good luck.
--
Keith Wootten
