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 memory and displaying the first screen. After this comes Second Stage Boot which involves initializing the program RAM, Mega CD Engine, 68k and CD Drive.
In order to get to First Stage Boot make sure you have 5V power when turned on and you have read the Power Circuit article to confirm you get 5V power when the Mega Drive is turned on.
Once you receive power, the next step is for the 68k and Mega CD Engine to load in the BIOS static splah screen without any text.
Dirt, flux and electrolyte that has leaked from capacitors can all cause no boot and issues. Warm up the board with a hot air station and clean with IPA and bamboo cloth while it is hot to remove all dirt and flux. Bath in warm vinegar to remove electrolyte then rinse in IPA.
I have seen several times simply the flux or electrolyte causing no boots.
Use the 240p Test Suite to confirm if most of the things needed for first stage boot are working.
The things that need to be working including all traces to and from them are:
- 5V rail
- 68k processor
- BIOS
- 50MHz Crystal
- Good Side Connector
- Bus Translator
In order to visually see entering First Stage Boot you also require:
- Word / Video RAM
- Mega CD Engine
- Working Mega Drive (test by entering 240p suite)
- Working AV lead (test by entering 240p suite)
If all tests pass on the 240p Test Suite then you should be able to enter at least Second Stage Boot (with the exception of the CD ribbon, the CD drive, and the Bus Translator and its traces which must be manually checked).
A great test is to use a flash cart and the 240p test suite.
Insert the flash cart into the Mega Drive while it is connected to the Mega CD and run the 240p test suite.
Make sure both the Mega Drive and Mega CD have power, and you have tested with the debug LED or multimeter the Mega CD does receive 5V when the Mega Drive turns on.
Then load up the test suite, and go into Sega CD Tests.
In here you will find a bunch of tests for confirming if the Mega CD is working.
You can test if the Mega CD BIOS is loading good. Run the BIOS CRC and info test. If the BIOS is good it will show a valid BIOS name and information.
The Program RAM needs to be valid and fully working to get past the blank BIOS screen. If the program RAM is bad, or the CD drive or ribbon, the BIOS will open up the background BIOS screen but won't load the logo or play any music.
Confirm the Program RAM is good using the 240p test.
The Word RAM (also known as Video RAM) are the two long chips near the edge of the board are two TC511664BZ chips.
If these are bad, you will see distinctive video glitches on screen. They will not prevent the Mega CD from getting to First or Second Stage Boot, and it will fully boot even without them, except you might not see anything on screen but still hear audio.
The Word RAM test often fails for me on fully working Mega CD consoles. So I am not sure how reliable the tests really are.
Do not confuse the WORD RAM with the WORK RAM.
The Word RAM is the two Video RAM chips (TC511664BZ) used for game loading and video data.
The Work RAM (MB8464A) is for saving game save data.
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