Re: [Re: [stella] miniaturization]

[Kevin Horton <khorton@xxxxxxxxxx>]

At 08:24 7/3/00 +0200, you wrote:

> >I think it's actually an enhanced SMS - I have the Master Base Converter,
> >which lets you play SMS games on it, and I'm pretty sure it's just a pin
> >converter (I can't see how much more complicated it would be when I paid 15
> >bucks for it new, not on clearance or anything.)
>
> >Then again, I don't know if there were some SMS cartridges I never had that
> >might have been too big for the GG/MBC to handle.
>
> Well, I studied the specs for these systems a while ago (the SMS video chip
> being a derivate of the TMS-9918 used in MSX, Coleco, and TI-99 machines),
> and it seems the Game Gear already has the Master System Mode built in, in
> which it will play the Master System games as usual. The "native" Game Gear
> carts, instead, use the Game Gear mode which isn't present on the original
> SMS. The Master Gear converter (that's how it was called here) thus only
> seems to re-wire the big SMS carts into the small Game Gear ones.
This is all it does.  There's a pin on the GG connector for GG/SMS 
mode.  Grounding it results in GG mode, while floating it results in SMS 
mode.  I have a GG dev cart which has this set up on a switch.  Needless to 
say, this can be fun to play with while a game is running :-).  You can 
click the switch while it is in operation and the GG game's play screen 
will shrink way down and the colours get messed up.  Clicking it back 
results in a normal GG screen again.  This has no effect on the game, which 
continues to run happily throughout the whole ordeal.  I need to burn an 
EPROM with an SMS game on it to see what happens when I put it into GG mode :-)

> It also seems to me that the TV Tuner hasn't got any software run by the
> CPU. However, one could check if it's possible to write a ROM portion for
It doesn't, AFAIR.  There's a pin on it that allows the input of RGB+synch 
on the connector, so anything that you plug in needs to output 
RGB+synch.  (The TV tuner has a composite to RGB decoder built in).

I do not suggest using the SMS for general A/V input, since the LCD is very 
low resolution.  The Nomad's LCD is very high resolution and 2600 stuff 
looks very good when played over it.  TV looks even better.  You can see a 
picture of my use of a Nomad LCD with an NES gut.

http://tripoint.org/kevtris/portendo.html

There's the link for Portendo with pictures of it in action.

----

As to using a Game Axe for something,  I recommend against it, since its 
LCD is very poor quality, at least resolution wise.  They double-scan every 
scanline on it so it looks "blurry".  There are only about 120 lines of 
resolution on it, so to make NTSC vid look fuller they scan ever scanline 
twice.  This results in very blurry and hard to read text on it.  I'm in 
the process of grafting a TFT LCD onto the Game Axe.  It looks possible 
since they used a standard modular LCD display on it.  Just remove the old 
and insert the new.  This may need some changes, circuit wise but shouldn't 
be *too* tough; the GA is built very modular with off the shelf parts and 
with plenty of empty room inside so mods are very possible.  First thing I 
want to do is replace that crappy 7805 with a switching 5V supply to save 
power.

----

As for making a portable 7800, this is a poor idea because the 7800 is very 
hard to program for, compared to say the Nintendo or GG/SMS.  Its scanline 
renderer is tough to work with no matter how you slice it.  Also, the lack 
of RAM and other stuff make it tough going.  As to why the Colour GB's LCDs 
are so cheap, it's because they are passive LCDs without a 
backlight.  Those quoted on Digikey are TFT with a CCF backlight on them 
(similar to what the GG or Game Axe has). The Colour GB's LCD has much more 
in common with the regular GB than say the GG's. 


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