[Coco] [Color Computer] Re: Japanese PC Game in CoCo Style?

[James Tamer]

> I own two TREKs (one boxed) and its version of the expansion
> interface.  It's one of the best built PCs in my 8 bit collection.  

I have one NEC Trek, and I'd agree with you, except for one thing:  
it runs hot.  It gets mighty warm, with the transformer in that 
case.  I never turn mine on without having an external fan blowing on 
it.

> The US version does
> have a better keyboard. 

We have the second generation keyboard.  I'm pretty sure the same 
thing was marketed in Japan as the PC-6001, a successor to the PC-
6000 which had the button keyboard.

> As far as CoCo 1/2 VS TREK... I think the TREK had some additional
> graphics capabilities by switching color mode with hardware on the 
fly
> so you could get more colors on screen at once but I've never been
> able to find docs about it.

This was implemented as a RAM array of 512 attribute bytes;  it was 
read in parallel with the screen RAM to provide mode information for 
each screen byte read.  The big purple-blue book that came with your 
NEC Trek talks about this.

You can mix and match modes on the
screen, with the caveat that putting incompatible things on the same
scanline causes undesirable effects, and the border getting its color
from whatever happens to be last on the scanline. The array wraps,
so it's read several times in graphics modes. The NEC Trek's normal
mode for BASIC is the extended characters, for which it has a ROM.
One downside is that the screen DMA cycle-steals or stretches, so the
computer runs at about 59% the speed you'd expect. There's a bit to
turn off the screen DMA, and then it runs full speed with the screen
blanked.

bit 0: (INV) Invert
bit 1: (CSS) Color Select
bit 2: (GM2)
bit 3: (GM1)
bit 4: (GM0)
bit 5: (_INT/EXT) Allows extended character set
bit 6: (_A/S) Semigraphics (64+32 = sg6)
bit 7: (_A/G) Full graphics

Virtual NEC Trek does not do a full implementation of the real video
weirdness. Maybe some day I'll revisit that. Still, I do a better
job of mixing video modes than the other two extant NEC PC-600x
emulators (or at least I did the last time I checked, which I admit,
was several years ago).

==
The SAM chip gives the CoCo some interesting new video abilities, 
which the Radio Shack tech manual calls things like "SG8" "SG12" 
and "SG24."  You won't find those in other computers (okay, clones 
and semi-compatibles like the Dragon do have these), since those 
aren't part of what the 6847 does.
==

> There is also a MKII and other follow up machine that were more
> powerful than the original including better graphics.

I also have a NEC PC-6001 MkIISr.  I suspect there's a kitchen sink 
in there.  Too bad the monitor I got with it was DOA.