Adding Sonic and Knuckle's "Lock-On Technolgy" with Sonic 2 and 3.
by No CARRIER
Logo-Free for your reading enjoyment.
Revision 1.02
"(Sorry for sloppy layout!)"
Lastest revision should take care of that!

How to play Sonic 2 & 3 w/ Sonic & Knuckle
With a Rom copy of each Sonic the Hedgehog game at hand, and a stable Genesis 
emulator ready to run, I guess it time for my to put that pulky Genesis and 
all those cartrages in the attic once and for all. Looking over the cartrages, 
I realized something, "How am I going to be able to play Sonic 2 and 3 with 
the Sonic and Knuckles 'Lock-on Technology'?" Hoping someone else would provide 
the answer, I waited... and waited.. and decided, "Hay, maybe I can figure 
this thing out myself," and I did!

What to do:

Its quite simple. First get a Rom copy of the three games. Then, at a DOS 
prompt, type:

COPY /B S&K.BIN + SONIC3.BIN SONIC4.BIN 
l          |            |            |
l          |            |            - Output name (Can be anything you wish.)
l          |            |
l          |            - Name of Sonic 2 or 3 Rom
l          |
l           - Sonic and Knuckles Rom name

You MUST do this at a DOS prompt. The "/B" does a binary copy. As far as I 
know, there is NO way of doing this from FIle Manager. (Thats why I choice 
the good old DOS system to run Console emulators over Windows.)

Why it works: My theory
Before I begin explaining why I think it works, we must make 2 assumtions.
1.) The program code and the modified graphics for Sonic 2 and 3 are located 
on the S&K cartrage. (I thing this is true because I don't see how the 
modifed graphics and all the changes in the program can be implimented on a 
"Ready Only Memory" medium.
2.) When you add a cartrage to the S&K cartrage unit, the Genesis treats it 
like one cartrage with a heck of alot of memory. In the sence of the ROM 
images, its just one large file. (Note, by combining them, the total size of 
the two cartrages is smaller than the largest ROM size possible that the 
Genesis can control.) Remember, it is doing this without the aid of 
additional handware, just software.

At power-on of the Genesis, after all the standard stand procedures are run, 
(Like master reset, ect.), the S&K cartrage looks to see if there is anything 
in the add-on port by trying to read the contents of the first bank or so. 
(It assumes that the smallest ROM size is under 1 Megabit or lower. So, by 
accessing a bank in this area asures that its going to read something.)

If something exists, it will get back some kind of feedback. 
 If it doesn't, it will get back all 1's or 0's because there are no banks 
 and it consideres them "blank". (The output would more likly be  "floating 
 high" 's.   I.e. all 1's)
  Since there is cartrage in the add-on port, it runs the Sonic and Knuckelsgame.
If it determines that add-on port is occupied, it will read the header of the 
cartrage. (Think of the head something like a file name: It's a means of 
identifing the cartrage if no lable was present.)

If it's not "Sonic the Hedgehog 2" or "Sonic the Hedgehog 3", then 
 it spits out the message "Ya right".
If it's "Sonic the Hedgehog 3" then 
 it runs Sonic 3 program on the S&K cartrage. 
It uses the Sonic 3 cartrage for all its graphics and sounds, except for any new ones.

At this point, if its not Sonic the HedgeHog 3 then it can only be Sonic the 
Hedgehog 2. So it runs the Sonic 2 program on the S&K cartrage. It uses the 
Sonic 2 cartrage for all its graphics and sounds, except for any new ones.

It doesn't work: What do I do?
From my tinkering around, Sonic 3 works fine with the S&K modifications, but 
you can't save any games. Sonic 2 does not work moment. It's more likly the emulator.
Also, check to see if the header says "Sonic the Headhog 2" or ..."3". Those 
console game distributers like to change the Header with things like 
"Sonic 2 for Console Zone" or "Sonic 2 supplied by ^BaTMaN^". Under my theory, 
this WILL cause problems. Find a program that lets you change headers of carts.

As for getting into the secret bonus level by using another cart other than 
SOnic 2 or 3, for the S&K cart:
no luck either.
__________________________________________________________________________
Need flow charts instead? Let me know and I'll create one if people want one.
Comments? Suggestions? Ideas? Need help? "Its doesn't work!" E-mail me, NO CARRIER, 
at wacko@tiac.net
or visit my web page at
http://www.tiac.net/users/wacko/

Go to "Emulation Zone" for the lastest updates on this stuff.

**** I will NOT respond to E-mail requesting Rom images, so don't ask! ****
*** The author of this page is not respondible for any damage caused by this 
procedure, no matter what. The author also has no realtions with Sega or 
Sega of America. USE AT YOUR OWN RISK.

Sonic is a registered tradmark of Sega 1991. All other tradmarks are 
trademarks of their respected companies.