GDEMU operation

Dreamcast can be powered on with or without SD card in GDEMU, and the card can be replaced while the console is running. To prevent Dreamcast from booting the 01 image automatically once turned on leave that folder empty and populate the card starting with 02.

[Early v4/v5 models only] IMPORTANT: Hold GDEMU board in place when inserting or removing SD card to avoid damage to connector and/or Dreamcast mainboard.

When SD card is inserted GDEMU will select image 01. To switch to next image on the card press the button beside card socket. Once the last image on the card is reached the device will jump back to 01.

It is possible to play multi-disc games by either storing all the images on the same card and selecting them with the button, or by swapping the cards.

There is a status LED on the GDEMU, it should blink once during power-up and then remain off. If the LED is lit, or starts blinking during gameplay, an internal error has occured. There are many possible causes of that, including SD card data transfer errors. The only way to restart correct operation of the device is to power-cycle the entire console. If the problem persists try a different card brand/size. If nothing else helps file a bug report.

INI file:

A simple text INI file can be put into root folder of the SD card to modify some of the GDEMU default settings. The file should be named GDEMU.ini.

IMPORTANT: Settings are read during SD card detection phase, so changing the card will result in GDEMU re-reading them again. This way it is possible to have different settings per card. If no INI file is found, the previous values will remain in effect.

Available settings:

  • open_time = N

Where N is natural number in range 150 to 5000, expressed in miliseconds. Defines how long GDEMU will idle with “lid open” status presented to the console after image change. Default is 500ms.

  • detect_time = N

Where N is natural number in range 150 to 5000, expressed in miliseconds. Defines how long GDEMU will idle with “busy” status presented to the console after image change. Default is 250ms.

  • image_tests = B

Where B is 0 (disabled) or 1 (enabled). If disabled, image integrity tests will be relaxed to allow oversized media. Note that correct operation is not guaranteed with such images. Default is enabled.

  • high_speed = B

Where B is 0 (disabled) or 1 (enabled). If enabled, GDEMU will transfer data from SD card in high speed mode . Note that this is an experimental option and might not work properly. Default is disabled.

  • reset_goto = N

Where N is natural number in range 0 to 9999. If enabled (N > 0), GDEMU will switch to image number N when it detects system reset. Default is disabled.