119
votes
Accepted
How exactly does Sonic & Knuckles' 'Lock-On Technology' work?
How does the Sonic & Knuckles cart detect another cartridge?
It checks the serial numbers of games; they can be found in the ROM's header. It probably detects all preceding Sonic the Hedgehog ...
- 1,838
40
votes
Accepted
How did people program for Consoles with multiple CPUs?
It varies machine to machine; at the simplest end is the Neo Geo — its 68000 and Z80 have completely independent buses. You write one program for the 68000 and one for the Z80 and a single pipe of ...
- 36k
39
votes
Accepted
How did the Sega CD decompress video?
We used to have to write our own video playback system, so each game did it differently. I worked on Microcosm for the SegaCD and if I recall we used a 16 colour palette for the video playback and had ...
- 516
32
votes
Accepted
How did the X-Men game for Sega Genesis have its state survive a console reset?
The reset button should clear the console's memory.
No, it shouldn’t. The 68000 reset vector is the first eight bytes in cartridge ROM. The cartridge will point at its own initialization code; the ...
- 2,230
29
votes
Accepted
Amiga 500 OCS/ECS vs Mega Drive VDP
The [pre-AGA] Amiga:
uses a planar frame buffer, stored in memory that is shared with the CPU (and which therefore reduces the CPU's speed);
provides dual-playfield hardware scrolling, but the total ...
- 36k
29
votes
Why was the Sega Genesis marketed as a 16-bit console?
... the Motorola 68000, was a 32-bit processor.
As already written in Raffzahn's answer, Motorola itself said that it is a 16-bit processor.
And as far as I know, the reason is not the external 16-...
- 3,389
19
votes
How did the Sega CD decompress video?
Playback of compressed digital video is handled entirely in software on the Sega CD which is why FMV games on it play with the video taking less than the full screen and at relatively low frames per ...
- 4,517
15
votes
Accepted
If the Sega Genesis/MegaDrive could be overclocked so easily, why couldn't the SNES?
The Super NES (SNES) has a much different hardware architecture than the Sega Genesis, and is built around the custom Ricoh 5A22 ASIC. As opposed to the discrete, stock, Motorola 68000 CPU employed in ...
- 60.1k
15
votes
Accepted
Why was the Sega Genesis marketed as a 16-bit console?
the Motorola 68000, was a 32-bit processor.
I'd say 16 Bit - likewise Motorola did (*1).
The bitness of a processor is and always will be up for discussion, as various features may not operate at the ...
- 213k
15
votes
How did the X-Men game for Sega Genesis have its state survive a console reset?
Similar methods have existed and are still used.
The reset does not clear the memory, it simply resets the CPU to start running code from start vector.
All the code needs to do is to check a known ...
- 28.3k
13
votes
How does Master System backwards compatibility work on the Megadrive?
The 68000 does nothing; it is entirely disabled. Ditto the Yamaha OPN.
The Mega Drive's VDP is almost entirely backwards compatible with that of the Master System — it implements the graphics mode ...
- 36k
12
votes
What is going on in the overscan area of Sega Genesis games?
Short answer: No. At least not for display purposes.
The pixels shown are artefacts when the VDP is operation in modes with more than 224 lines (NTSC). These lines were usually not displayed on real ...
- 213k
12
votes
How did people program for Consoles with multiple CPUs?
There are two basic techniques: shared memory and dedicated communication ports.
Shared memory simply allows both processors to access the same memory bus. There are some issues, as the bus has to be ...
- 15.1k
12
votes
How did the X-Men game for Sega Genesis have its state survive a console reset?
The reset button should clear the console's memory.
Why? And who should do that?
The Mega Drive is a very classic console. There is no OS or monitor (*1) that controls execution and prepares the ...
- 213k
11
votes
Amiga 500 OCS/ECS vs Mega Drive VDP
The Megadrive comes from an arcade machine lineage, it's cut-down Sega arcade machine hardware. The Amiga comes from a computer lineage, it's an evolution of the Atari 800, same designer, and many of ...
- 410
10
votes
What is going on in the overscan area of Sega Genesis games?
The color RAM in the Genesis video chip is single ported such that at any given time the color RAM data bus either contains the data being read out of it for display purposes, or the data being ...
- 1,510
10
votes
Accepted
Using the (An)+ to Memory addressing mode when address register is pointed to ROM causes Sega Genesis DMA to fail
I can't believe I only see this topic so long after it was post !
For reference: I made the 68k optimizations of the video engine of a recent and quite famous game.
The Genesis Software Manual scanned ...
- 659
9
votes
Why was the Sega Genesis marketed as a 16-bit console?
It's usually the width of the system data bus that determines the "bitted-ness" used to describe the system.
While the Motorola 68k CPU used as a component in the Sega system certainly has some ...
- 60.1k
9
votes
Accepted
Graphics Editor for 16-Bit Games
Depending on the platform we're talking about, you've got a few choices. As the best platform for editing images at the time was the Amiga with its 4096 color palette in HAM mode on OCS/ECS (Original ...
- 1,017
9
votes
Accepted
What ended the Sony console partnerships with Sega and Nintendo?
There was a relationship between Sony and Nintendo starting in 1988 and into the early 1990s as someone in Sony was looking to get into the video game business after seeing how successful the Famicom ...
- 15.8k
8
votes
Accepted
What cleaning/repair can be done to a Mega Drive cartridge slot?
Have you tried cleaning the pin connector inside the Mega Drive? It's fairly simple to remove the shell and access the pin connectors. (don't forget to remove the LED wires for model 1) I got a second ...
- 919
7
votes
Accepted
Sega Genesis and Sega CD interaction
To answer the first half of your questions:
The right-side 60-pin expansion slot is bespoke, and found on Mega Drive / Genesis 1 and 2 only. It is not present on the Genesis 3 or Nomad.
It exposes the ...
- 11.8k
6
votes
Sega Genesis/Mega Drive ROM Disassembler
DGEN emulator has a starscream 68k core with a builtin dissasembler and debugger . ` might be the key to break into it once rom is running. It's also easy to recompile with SDL as the gfx/audio ...
- 61
6
votes
If the Sega Genesis/MegaDrive could be overclocked so easily, why couldn't the SNES?
It's an issue of integration. On the early Genesis systems the custom chips and CPU were physically separate from each other so it was easy to isolate the various clock signals and replace the CPU ...
- 1,510
6
votes
Self-modifying code in commercial games for the (S)NES, Gameboy, Genesis/MD, PC Engine, Atari, etc
RAM and ROM are reachable by the CPU for execution, so most consoles can execute code from RAM.
The consoles using cartridges usually don't have a lot of RAM, so I think it's VERY rare if someone ...
- 10.7k
6
votes
Accepted
Self-modifying code in commercial games for the (S)NES, Gameboy, Genesis/MD, PC Engine, Atari, etc
I know about one Atari 8bit game called Robbo. There are source codes published where in file R1.ASM you can see:
LDA LMVT,X
STA JMP1+1
LDA LMVT+4,X
STA JMP1+2
JMP1 JMP *
LMVT ...
- 257
6
votes
Self-modifying code in commercial games for the (S)NES, Gameboy, Genesis/MD, PC Engine, Atari, etc
I rarely had occasion to use self-modifying code. Doing that had a lot of overhead both in ROM space and RAM space, and I rarelysaw an occasion where it would be worth it. I did do it on the IBM PC, ...
5
votes
Amiga 500 OCS/ECS vs Mega Drive VDP
TL;DR:
For all of this it might be helpful and take a step back from bits and bytes and take a step back to look at the whole process of Game development. Doing so will show that quality is much more ...
- 213k
5
votes
Building a Sega Genesis Classic Portable - What kind of display?
In the video you linked (at 01:12), I notice that this device has the standard yellow and white connectors for composite video and audio. Many cheap portable LCD TVs support this kind of input, and ...
- 8,036
5
votes
"Genesis Lock-On Technology" to change the language of a Famicom game
I'll assume you only want to modify small parts of the game, rather than the entire game. (If you wanted to modify the entire game, you'd just make a new cartridge holding the entire image.)
Your ...
- 246
Only top scored, non community-wiki answers of a minimum length are eligible