Sonic and knuckles rom how to#

I like to think of them as a 'base' and 'limit register', which are found in most modern CPU's. If there is any, it will also specify the range of this memory in the form of a starting and ending I/O address. The data from 01B0h to 1BBh of the ROM header specified weather or not any external memory (ie, SRAM) is available. This step will require some hex editing of the header of the combined S&K3 ROM image. So now, as you can imagine, the solution is to make the emulator think that SRAM exists in the S&K cart.

However, not all carts use SRAM, and the data stored here could be as meaningless as random mumbo-jumbo. It might seem foolish for an emulator author not to store any data in a band of memory primarly used for SRAM. Since the emulator does not know that SRAM exists, it does not bother to emulate SRAM by saving its data to disk. Once you exit the emulator, the data in emulator's memory is lost, which means that the data in system RAM, VRAM, etc, is lost as well. It will become the task of the emulator to assure that the newly written piece of data is accuratly acted upon within the emulator, whether it be used to control an I/O device or lay simply as data. So if a game requests to write a piece of data to SRAM, the emulator will record the new data and register it in the emulators's memory. An emulator will register any data written to/from any band of memory and record it in its memory SRAM is no exception. This circuitry ensures that whenever a request is made to access SRAM, the cart in the expansion port, namely the Sonic 3 cart, will receive it.ДЇrom a programmer perspective, any Genesis hardware, weather it be a register, system RAM, ROM, VRAM, or even SRAM, is accessed by addressing memory within a certain range (band) of memory. If you examine the circuitry of S&K cart, you will notice that the S&K cart passes all of its data and address lines to the cart in the expansion port.

Sonic and knuckles rom how to#

To understand why this is a problem, and how to provide a solution, we need to understand how SRAM works. This problem is attributed to the fact that the S&K ROM header does not explicitly specify that SRAM exists. (Give this a shot with the real game carts and with an emulator!)Д«ut alas, there is a problem! If you try to save a game with a generated S&K3 ROM on an emulator: it doesn't actually save the game to disk. The fact that they don't over write each other's save states proves that one was written with the other in mind.

If you save a game in Sonic 3 and then try to save a game at the same location with Sonic 3 Locked-On to S&K, you will discover that the location in question is blank or contains a different savestate altogether. The most obvious piece of evidence is how the SRAM chip in the Sonic 3 cart is utilized by Sonic 3 and S&K. For more information on how to expose these hidden levels, visit Tom's Sonic Hacking station. The biggest piece of evidence is the existence of some of the levels of S&K within Sonic 3. This can be accomplished with some cleaver hex editing of a save state associated with that location in the game. One example is the ability to select Knuckles from the character select screen in Sonic 3. The reason for this is because there is evidence that Sonic 3 was designed to be associated with S&K ROM sometime in the future. Stealth, Tom, and a few others have called the Lock-On Technology a sham. This innovative new idea brought some fresh new life to the Sonic line of games in a manner none have seen before! Never the less, implementing this concept with Sonic 2, a game which was already on the market, was not an easy task. In fact, it is believed that the levels in S&K3 were originally planed for Sonic 3. Sonic 2 was patched to enable Knuckles by using a hidden 256k ROM within the S&K cart. It was rumored that Sonic 1 had a glitch that crashed the game if Knuckles glided onto a conveyor belt, so a 3D bonus level game was created instead. There is nothing magical or revolutionary about the 'Lock-On Technology. This is all accomplished using some new technology called 'Lock-On Technology.' Attach Sonic 3 to transform S&K into a huge 32-Megabit epic with a more intensive story line and over a dozen total zones to explore! Attach Sonic 2 and take advantage of Knuckle's special moves to discover secret powerups and hidden passages. We hope you find this information useful!Д«y merely placing any Sonic game into the Lock-On port of the S&K cart, one will be able to play as Knuckles within that game. This document is intended to provide a complete technical documention of the Lock-On technolgy found in the SEGA game 'Sonic and Knuckles.' The information in here comes after years of on and off research from many contributors, including myself. This document is meant to help you better understand the 'Lock-On Technology' used by SEGA for it's Sonic & Knuckles game.