There’s a new firmware available for GDEMU that fixes the slightly muted sound issue that some Dreamcasts had. I took this opportunity to introduce some more code changes so please report any regressions and/or new bugs.

Several Rheas have already been delivered and these are very common questions:

  • 50/60 Hz auto-switch

There is a solder point on the PCB marked “Hz“, and a solder jumper marked “Select“. You need to route a wire between the Saturn’s chip lifted pin and the Hz point, plus solder the jumper to select the default setting. This however is not yet working (the current FW doesn’t even support it) so leave it be for now. It’s coming soon, I need to test this first to make sure it works as expected.

  • Region patcher

Rhea is region free as is GDEMU – in the sense that it doesn’t care about regions at all. The lockout is enforced by BIOS, not the drive. You can however either patch the images yourself (there are tools for that) or have Rhea do it for you during game detection/loading. To enable that you need to tell it what region your console is – create ASCII text file named “Rhea.ini” in the root folder of the card, then place the following entry in it:

auto_region = N

where N is the code for your console region, or -1 to disable the patcher (the default setting). The codes are:


Email me if you find a game that’s not working when patched.

Ages Three and Up

This is a short explanation on how to install Rhea V3 properly – I’ll try to make it into a permanent page later on but for now this will have to do. Note: This is meant for people getting their Rheas soon, comments will most likely be ignored.

Installation is easy but not as trivial as with GDEMU. You’ll need some wit and technical skills (nothing fancy though) and a soldering iron. Disconnect your Saturn, unscrew and remove the upper cover. Disconnect and remove the drive. It can be lifted a bit, I found it makes it easier to remove the flat cable that way, but be aware there might a thick wire or piece of copper foil screwed on top to provide better ground connection. Carefully disconnect that first (you’ll need a fine Philips head screwdriver).

You will need to locate +5V power supply spot on the motherboard and solder a wire there to provide power for Rhea. Unfortunately the connector is difficult to source and the original power cable is tad bit short anyway. Better yet route 2 wires, 5V and ground, but GND is somewhat optional as there are a few connections through the flat cable and that should be enough. I’m not providing any pictures as to where to tap into 5V on the motherboard – this is on purpose. I don’t have good photos of all possible motherboard variants, and I want you to check that yourself using a volt meter. Best solder the wire on the opposite side of the PSU connector (or even PSU itself) but be aware it’s harder to do as there is plenty of copper to take the heat away and that makes soldering a bit more difficult. Rhea doesn’t draw much, maybe 250mA with the card, so it’s not all that critical.

Rhea V3 PCB is clearly marked with what goes where when it comes to power supply, you have 4 holes: 2 upper ones are 5V, 2 lower ones are ground. You just need to solder to one of each. You can also install pins and make a connector if you wish for easier removal. See the bottom left corner of this photo:

RheaV3 - installed

I need to point out that Rhea can also be powered from external PSU (like wall cube or something), just make sure it’s got clean 5V output. Obviously that will need 2 wires. The nice thing about this setup is you can swap Rhea much easier and there’s no need to solder to the Saturn motherboard. It’s up to you though. In case of external PSU it needs to be plugged in first before you power on Saturn, and you can safely switch Saturn on/off for short durations while keeping Rhea powered. You can for example add/remove the 4MB cart during that time. Rhea, as long as it’s powered, will keep the selected image.

If you have a copper GND foil (or a wire), as seen on the photo, remove it. It’s held down by a single screw. There is a risk it will come into contact with the voltage regulator on the back of Rhea’s PCB and cause a short. I keep it in my unit but then again I understand the risks of being careless 🙂

The photo above also shows how to connect the attached flat cable. Note it goes into Rhea conductor-side down. This is the reverse of most drives and it’s also on purpuse. The connector is much closer to front now and you can user either the cable provided, or the original one:

Saturn 20-pin flat cable

Just bend it in the middle (but don’t flatten it, no need for that, there’s plenty of room inside Saturn). Note that the original cable has clear ends, unlike the one I’ve attached. The connector on Rhea is a ZIF, it needs to be opened by pulling the latch, the cable inserted, and then secured by pushing the latch back (which actually does require some force but not much). Make sure the cable is all the way in. Same for the motherboard side.

In case your Saturn model has the motherboard connection near the right side (rather than near the front) the procedure is the same, just twist the cable to make it fit. The plastic supports are optional but highly recommended, I’ve included 2 and you can mount one (especially near the button) or both.

The FW is being worked on, the one in the units is already outdated and has known issues with some games (missing or cut short CDDA). You’ll get upgrades once I’m satisfied with the results.

Lastly, if there is anything unclear, ask me first. By email.

Heigh-ho, Heigh-ho

The parts I needed for GDEMU have now arrived but I’m already a week behind schedule, and I still have to actually make and test the devices so that’s going to be another week at best. Shipping anything during that time is pretty much guaranteed to take much longer than usual to arrive due to general Xmas shopping spree, in fact you’ll be lucky to get your GDEMU in 2014 still. What’s more, it turns out I will be away from home, visiting family. That means no games will be played, er, I mean no GDEMUs will be made anyway during holiday.

Very sorry about this but at this point there’s simply nothing I can do.

I should be able to deliver the early Rheas though, I have one fully assembled (but not yet even programmed) and the rest should be ready in few days if there are no problem with the first unit.


The gold on black looks nice, doesn’t it? I might go that route for some of the last GDEMUs as well.