Dreamcast details

There are three known Dreamcast variants:

  • VA0 – early production
  • VA1 – ~99% of all consoles
  • VA2.1 – late production

NOTE: VA0 and VA2.1 are NOT compatbile with GDEMU. While it can be installed inside VA0 model and will appear to work, it is not safe and will eventually result in damage to the device and/or console itself.

VA0: Found mostly in JP region, though some US consoles exist as well. Uses slightly earlier motherboard revision with temperature sensor, heat pipe and metal fan cowl (some sources say it’s because it heats up more). Has earlier BIOS version but most importantly both the BIOS and FLASH chips are 5V devices and output 5V on the G1 bus – which is not safe for GDEMU.

VA1: Most of the Dreamcast production run was VA1, nothing special about it 🙂

VA2.1: Some late models that have the drive logic integrated into the motherboard – thus it is not possible to connect GDEMU anymore. Note that the drive unit is different between VA0-VA1 and VA2.1 and cannot be swapped either.

Unfortunately for JP region consoles there isn’t any easy way to tell these differences apart unless you open the console and look inside. You should do it anyway in case the internals have been swapped due to repair for example.

NOTE: All the internals can be swapped between Dreamcast cases, in other words a VA0 or VA2.1 inside a rare/custom case can be replaced with VA1 mainboard, making it compatible with GDEMU.

Known issue – all Dreamcasts suffer from a poor connection between the power supply (PSU) board and the mainboard. This is typically caused by oxidation of the metal pins on the mainboard and gets worse with age but most of the time can be easily fixed, see below.

GDEMU has undervoltage detector that will cause it to reset itself and blink the status LED if the 3.3V line drops below 3V. This is on purpose, most SD cards will not work properly with unstable power supply and this issue cannot be easily detected otherwise. Typical effects include:

  • random game hangs (note: these can also be caused by SD card itself)
  • random resets/reboots
  • sound “too slow” and/or wrong pitch, or missing completly
  • GDEMU status LED blinking randomly

NOTE: Sometimes the original drive will appear to work in a given console but GDEMU wont. This is because neither the drive nor the mainboard have any sort of undervoltage protection – however this configuration will not be stable and will eventually also start randomly resetting itself and even fail to boot at all .

The fix is simple and can be done by anyone capable of installing GDEMU:

  • disconnect all cables from the console
  • unscrew and remove the upper part of the case
  • unscrew and remove PSU board (there is also a plastic latch holding it in place)
  • wipe the metal contact pins sticking out of the mainboard well with a clean cloth
  • assemble everything back and test

Small amounts of alcohol on the cloth can help remove any contamination, however do not use any aggresive solvents or acids, or sand paper instead of cloth. The issue can be made worse if improper repair is attempted and the spring contacts in the PSU are bent, or the pins are treated with abrasive material and the anti-oxidation layer is completly scraped off.

Worst case scenario the PSU or mainboard might need to be replaced. Alternatively the pins and PSU connector can be desoldered and replaced with wires – it’s not as easy but will permanently fix the problem (provieded the PSU is not faulty to begin with). Note that attempting to solder the pins and the connector contacts together usually ruins both while not actually providing a good connection (the solder tends to break off after a while).

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