Sega Mega CD
Sub-pages
Capacitors (Sega Mega CD)
The Sega CD (Mega CD in Japan) v1 is the first model of Sega's CD-ROM add-on for the Mega Drive/Genesis, released in Jap...
Hardware Overview (Sega Mega CD)
The Mega CD circuit is mostly made up of the following chips: 68000 CPU (Motorola MC68000) Program RAM (512kb) for 68000...
Board Scans (Sega Mega CD)
You can find complete PCB and schematic redraws for all revisions here . This is great for allowing tracing of connecti...
Power Circuit (Sega Mega CD)
The Mega CD / Sega CD has a power circuit that is enabled when the Mega Drive / Genesis provides 9V power through the ...
Side Connector (Sega Mega CD)
The connector block that joins the Mega CD to the Mega Drive has several versions, and it must match the Mega CD motherb...
Boot Up Diagnostics (Mega CD)
To help diagnose what is wrong there are a few common issues that can help pin-point an issue. Make sure to use a known ...
First Stage Boot (Mega CD)
First stage boot is getting to the BIOS screen without any text displaying. This means the BIOS has been loaded into mem...
Second Stage Boot (Sega Mega CD)
Once the BIOS has been fully initialized it then loads the BIOS program into Program RAM, makes communication with the C...
Third Stage Boot (Mega CD)
Once you get to Second Stage Boot (the Mega CD BIOS screen to fully load with logo, disc tray opens and game starts to r...
Delayed Boot Issue (Mega CD)
This covers a very specific and easily misdiagnosed fault: the Mega CD hangs at First Stage Boot (the background BIOS ...
Random Static Noise (Sega Mega CD)
A fault I see fairly regularly is a snow / static type noise appearing over the screen once the Mega CD has booted. It t...
Mega CD Engine Pinout (Sega Mega CD)
The Mega CD Engine, also known as the Gate Array, controls reading in and generating the overlay graphics used on top of...
Stuttering Skipping Audio (Sega Mega CD)
A common issue I have come across is when the Mega CD loads up, but it is as if every half second the sound cuts out, cr...
Game Save (Sega Mega CD)
The game saves are stored in the Work RAM (MB8464A, IC16). This Work RAM is enabled by the CS2 pin, which is controlled ...
BIOS File Headers (Sega Mega CD)
A useful resource when dealing with BIOS files is to know how their headers look so when you open a binary dump you can ...