P21H Experiences

[lowry@xxxxxxxxxxxxxxxxx (Dave Lowry)]

Louis Frazier writes:

>>I have run mine for more than 100 hours at 5.6 volts. I found I couldn't
>>make it work at 5 volts, so I took an old regulated supply and soldered in
...
>>until it smokes before I fool around with trying to run it at 5 and the
>>p21 at 5-7.

My '21H board wouldn't do serial i/o properly below about 5.8 volts.  I think
running the various chips at different voltage levels is a *bad* idea, as P21
will be sending out logic levels above the Vcc of the other chips.  Most chips
don't want to see inputs much above their supply voltage.

>>I've been running on an old apple green monitor, and it is all I need for 
>>geometry. Hwever, when I try to run on a color TV with monitor inputs I 
>>only get B&W. Before I go to a lot of expense to get an ntsc monitor, I'd 
...
>>The display is pretty jumpy, and I don't see any difference when I run T's
>>routine to slow the I/O.

Works on my color TV.  Be aware that there's lots of chroma crawl (dots that
crawl around vertical edges) on many of the colors P21 generates.  It can
be very ugly.  I stick with the gray and dark blue.  Also, my '21H kit exhibits
a degree of chromatic flashing in addition to the little serrations caused
by the slow i/o.

>>I have figured out how to run the metacompiler and as soon as I get an

Had my first metacompiling experience this weekend by running Ting's
metacompiler.  Compiled in an eyeblink, literally (100 MHz Pentium).
Knocked my socks off.

>>I would like to switch screens by programming video jumps, but this whole
>>area is hard to follow.

Jeff Fox has done this with his very excellent P21Forth.  Unfortunately,
he hasn't ported it to the '21H board... which one wouldn't expect he'd
do gratis.  So, I'm willing to pony up $50 for a port.  Anyone else willing
to make this worth Jeffs time?

Really, folks, eForth is *dog slow* compared to P21Forth.  Plus, P21Forth
is ANS, and has many nice added features like double buffered screens and
variable text window sizes, etc.

>>I draw on the PC screen using Ghostscript, a public domain version of
>>Postscript. I see the possibility of developing postscript-like functions
>>to draw on the P21 monitor.

>>   Has anyone done this, and is the code available?

>>   If not, where can I find floating point and trig functions in Forth,
>>   free, which will run in eForth on P21.

Well, a few years ago I did a wireframe 3-d graphics package.  Rotation,
scaling, translation, perspective, 3-d clipping, etc.  Works for 2-d too.
Mostly high level Forth, but a few good CODE words for very fast line
drawing.  It's called OKA3D. :-)  (Thanks, Penio!)
Unfortunately, it runs on Jeff's P21Forth only.

>>Any comments or suggestions welcome. Especially from people working with
>>the same board at a higher skill level.

Just another Forth newbie trying to bend my brain around P21.  Some days I
can't decide if Chuck Moore is the world's smartest man, or if he's some kind
of evil prankster. :-) :-)

-Dave