Originally Posted by
SMS Faq
The official word: No. The unofficial word from curious hackers: I don't
see why not. The NEW unofficial word: No, due to color conflicts. Here's
some information I received (from Meet Mr. Malaria (kyoshiro@netcom.com)):
"As for the possibilility of running Game Gear games on an SMS,
I'd say no, or at least a firm possibility that it can't.
The Game Gear can run SMS carts, of course, but that may very
well be due to intentional downward compatibility of the GG to the SMS,
and such may not work in reverse. The only hardware [difference] I know of
between the two on a chip level is that the GG has a 4096 color palette,
while the SMS has a 256 color palette, but that may be enough. If the GG
has a larger palette, than it must have a different method of setting
each of the color registers than the SMS did: The SMS color can be
determined by one byte, so probably only needed one register, whereas a
number from 0 to 4095 needs two bytes, and therefore the GG chips
probably have two color registers, or one register with a special system
which allows both bytes to be written one half at a time.
The Game Gear was probably designed to allow the color registers
to be set by either the 256 color method (for downward compatibility), or
the 4096 color method, whereas the SMS was created before the GG, so it
would not support a GG-specific game's method of setting colors.
The possible problems resulting from this incongruety -alone-
might be:
#1. A complete crash (if the GG game tried to set registers that did
not exist or had nothing to do with color)
#2. Completely scrambled colors (if the GG uses the same registers
to write the colors, but in a different way)
#3. No picture at all (if the GG writes colors using registers that
had no function in the [SMS], so no SMS color reg would ever be written
to, and all would default to black, so no picture)
It may still be possible that the two are still compatible, but
only [if Sega] intentionally created the GG to set colors in a matter that
would cause the [SMS] to use it's nearest approximation, or if each cart
were programmed to be SMS compatible.
Summary: It looks to me like the GG was designed to be downwardly
compatible with the SMS, but the SMS would not have been designed to be
compatible with the GG."
-- BUT --
From Richard Holbert :
"I don't own either, but I read your FAQ and have an idea that might work.
Aside from the obvious hardware interface problems, the software
incompatibilities could be addressed as follows: I think it should be
possible to rewrite the SMS BIOS ROM (or whatever Sega calls it) to map the
extra color codes to their nearest SMS equivalent.
Source code for both SMS and GG BIOS would be very helpful, but someone
could probably disassemble them."
Someone once mentioned that a pre-Christmas '92 issue of VG&CE contained a
mailorder ad offering a GG to SMS adapter, but my VG&CE collection is
incomplete, and I haven't been able to confirm its existence. Any
information is welcome.