The Sonic Genesis ports

In 1997 Sonic Jam hitted Sega Saturn. It was all the Sonic games from the Genesis and some people believed they were emulated and other ported.

For people like me, Hivebrain, and JoseTheBest who has a really deep knowlege of the Sonic engine knows that it was specially designed to work on the Genesis only. Some people still believe the code was written in C or C++ so it could easily be ported to other systems.

So what's the truth? How could 4 Sonic games be ported into a new system just like that?
Well, it's because in 1996-1997 no emulators existed. No one had developed a way to emulate the games. Sonic Team used some kind of a convertor to convert the Motorola 68000 code into HITACHI SuperH-2 RISC Processor code (for Sonic Jam) and into Intel i386 processor code (for Sonic & Knuckles Collection PC).
The rest such as data managing and the way to display the art was developed for each system to emulate the VRAM and display planes as easily as possible.

Just look and compare some code from S&K Collection PC and the original Sonic & Knuckles shall we:

The Penguins in Ice Cap Zone (Object AD) Original 68000 instructions (Genesis):

Code (Text):

1. pngn05_init:
2.     move.l  #pngn05_pt, 12(a0);- Pattern table
3.     bset    #2, 4(a0)  ;- On playfield
4.     move.b  #$20, 7(a0)  ;- 32 px width/2
5.     move.b  #$20, 6(a0)  ;- 32 px height/2
6.     move.l  (a7)+, 52(a0)   ;- Snow link from stack
7.     move.l  #pngn05_pg00, (a0);- Next action
8.     ...

The Penguins in Ice Cap Zone (Object AD) converted i386 instructions (PC):

Code (Text):

1. pngn05_init  proc near
2.  
3.     mov  eax, offset pngn05_pt
4.     mov  edi, A0_ptr
5.     mov  [edi+12], eax  ;- Pattern table
6.    
7.     mov  edi, A0_ptr
8.     mov  eax, [edi+4]
9.     bts  eax, 2
10.  
11.     mov  edi, A0_ptr
12.     mov  [edi+4], eax  ;- On playfield
13.  
14.     setb    al
15.     and  al, al
16.  
17.     mov  al, 20h
18.     mov  edi, A0_ptr
19.     mov  [edi+7], al    ;- 32 px width/2
20.  
21.     mov  al, 20h
22.     mov  edi, A0_ptr
23.     mov  [edi+6], al    ;- 32 px height/2
24.  
25.     pop  eax
26.     mov  edi, A0_ptr
27.     mov  [edi+34h], eax  ;- Snow link from stack
28.  
29.     mov  eax, offset pngn05_pg00
30.     mov  edi, A0_ptr
31.     mov  [edi], eax     ;- Next action
32.     ...

As you can see, the converted code uses a variable called A0_ptr to emulate the A0 register pointer on Motorola 68000.
The same goes for all other Address registers and Data registers. So there was nothing more than a cheap code conversation to make the Sonic games appear on the other systems.
So the true Sonic (even Sonic 1 with Spindash) will forever be specific Genesis Motorola 68000 assembler. Without this system it won't be Sonic.

/LOst

 

Just emulators. Nothing different in the ROMs. No new source code. Just hacked ROMs like we can do ourselves.

 

Sega could have been better if they hadn't lost the code. Now they have to do ROM hacking like we do to get stuff like spikes to work in Sonic 1 Mega Collection.

 

If they could use Gens. But they can't without giving out the source with it.

They uses the old Kgen. No Sega CD emulation existed then

 

For some reason they didn't.

I don't like discussions about what they can do when there is no proof they can at all.

 

They are not just fans :P

They are crazy motherfu*kers who make emulators for fun