Re: Recent dialog and old initiatives
Myron Plichota wrote:
>
> Ben,
>
> I enjoyed checking out your website. It looks like you are a fan of the
> PDP-8 and Nova CPUs. I think they are kind of cool too. From what I can your
> goal is not to produce a Forth chip. I am sometimes torn between a pure
> Forth and a more general-purpose approach, but I always seem to come back to
> Forth, or at least some kind of stack machine.
My goal is to produce a General Purpose TTL based computer. Since TTL
is hard to come by nowadays I am using FPGA chip and TTL macros. Unfortunately
I have been hard pressed to find room for the minimum Forth instructions: CALL
and 0Branch. My other goal is to keep things 'lite' and Forth machines have a
lot of good idea's here.
A real Forth machine which has both stacks implemented
> on-chip as shift registers yields very fast execution of fundamental Forth
> stack operators with a minimum of transistors but at the price of making
> stack indexing or re-ordering operators such as PICK very inefficient and to
> be avoided at all costs.
This is true with any implementation of Forth. The General purpose machines
also have a hard time with the large amount of subroutine calls in Forth
as the Cache keeps getting reloaded.
>I have not yet had the pleasure of running a real Forth
> machine yet, but I now write Forth on my PC in a style heavily influenced by
> x21 precepts. There are so many good general-purpose architecture CPUs
> available that I am not very interested in building my own.
That is a matter of often long debate, of what is a good cpu architecture.
RISC machines to me use too much memory bandwidth.
> Also, it's usually quicker to
> simply type " x <= a and not b;" then to browse for the equivalent schematic
> symbol (and create it if it doesn't exist), and then point and click all
> over the place to establish its place in the design.
At the moment using a 74382 alu macro is a simpler than figuring out the
VHDL code for a ALU.Once I get a working schematic version then I will
rewrite for a high level language.
--
"We do not inherit our time on this planet from our parents...
We borrow it from our children."
"Luna family of Octal Computers" http://www.jetnet.ab.ca/users/bfranchuk
