Preferred Threading Model for F21/i21? 
Author Message
 Preferred Threading Model for F21/i21?


Quote:
>What is the preferred threading scheme for Forth engines like
>F21 and i21 that have "lots" of stack?

My understanding is that they don't have that much stack -- five to eight
cells, that's all.

--
-William "Billy" Tanksley
"But you shall not escape my iambics."
           -- Gaius Valerius Catullus



Mon, 03 Sep 2001 03:00:00 GMT  
 Preferred Threading Model for F21/i21?

Quote:

>My understanding is that they don't have that much stack -- five to eight
>cells, that's all.

No, F21 has like 16 to 18 cells each for return and data stack.

P21 had the 5 or so.  That's why I posed the question.  Threading
in P21 wasn't that efficient since the stacks were off-chip.  I
was wondering what the best NEXT and colon-def entry would be if
one assumes the 17 or so is deep enough not to have to keep the
stacks off-chip.

-Dave



Mon, 03 Sep 2001 03:00:00 GMT  
 Preferred Threading Model for F21/i21?


   :What is the preferred threading scheme for Forth engines like
   :F21 and i21 that have "lots" of stack?

Still none. :> You can build a "normal" Forth a lot faster using
subroutine threading than any other way, as far as I understand it. You
just define a lot of subroutines and macros, to cover the words that the
F21 doesn't have.

But if you really want threading:

Indirect threading, code in SRAM/ROM:

   do:   = A PUSH NEXT

Direct threading, code in SRAM/ROM, separate list space:

   do:   = # ~addr >R NEXT

Direct threading is perhaps a little faster overall, but for code
locality it's possible that indirect threading wins. You really want
code in SRAM, otherwise the off-page accesses will slow things down
quite some way. ...But it really isn't worth it, imho.
--



Tue, 04 Sep 2001 03:00:00 GMT  
 
 [ 4 post ] 

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