There are a number of hurdles to consider when building a portable Nintendo 64, including:
- Power management
- Heat management
- Cartridge slot relocation
- Video output
- Controller / case design
The N64 power brick has only two output voltages, 12 and 3.3V. The former is used for composite video output, the audio amplifier, and a few other things while the 3.3V powers the controllers, CPU, RCP (GPU) and RAM. The 12V line drops down to 5V through a 78M05 regulator, so just about any battery above 6V will power this line. The 3.3V line must be regulated tightly so a decent DC-DC converter does the trick. You’ll need one able to supply at least 3 Amps.
It’s also possible to undervolt the 3.3V line slightly to reduce power consumption and heat generation. The N64 RDRAM datasheet quotes a minimum voltage of 3.0V. Although the CPU might not be stable with this, it’s a good figure to aim for.
The Nintendo 64 heatsink is enormous. You can get away with almost any northbridge heatsink if you use good thermal compound. I opted to flatten the stock extruded Aluminium heatsink which brought it down to size and still kept the processors reasonably cool. A case fan is a necessity. The N64 expansion pak absolutely requires a heatsink.
Cartridge slot relocation
I used IDE cable to relocate the cartridge slot. To do this, you need to cut away the RF shielding from the underside expansion port (used for the 64DD) and pull it out. Then, the cartridge slot should come loose.
For video output, a popular device is the official PSOne LCD screen. I grabbed one of these off eBay, removed the LCD and control board from the plastic casing and directly wired the composite, audio left and right inputs to the N64’s outputs. The LCD was also happy with the 7.2V input. Simple! I also disassembled the LCD itself, and replaced the CCFL backlight with four super-bright LEDs to reduce power consumption. ExtremeTech has a great LED installation guide.
Controller / case design
I designed a case on my computer, and prototyped it with cardboard. Once I was satisfied, I rebuilt this with some UV-treated PVC sheet. Speaker, button and power / switch holes were drilled using a drill press. The screen area was cut with a jigsaw. I also moulded the Z and R grip sections of a N64 controller to the rear of the case, using a combination of Selley’s Knead It putty, followed by some Nitrocellulose filler (the same goop used to fill small dents in car bodywork). Finally, after many hours of sanding for a smooth finish, I painted it with some vinyl paint. The metal trim is stainless steel bent to match the panel design. I made four screw posts from Aluminium tubing, and epoxied small catches on the inside of the metal trim. The two panels sandwich the trim and screws hold everything together. It allows me to disassemble the case completely should I have to repair the electronics.
I split the controller board up and wired directly to the control chip. Doing this allowed me to use the nice rubber membrane buttons rather than resorting to tact switches. Wiring the controller sections up was tricky. Soldering IDE cable to the controller contact board would obstruct the buttons, so I used enamel copper to loop around to the back of the board, followed by IDE cable to reach the encoder portion of the controller board. This wasn’t a great solution but it’s working reliably.
It’s pretty big and heavy but I’m happy with it nonetheless. If I were to do this again I would be less cautious about heat management, which would allow me to build a smaller case. I’d also use flat Li-ion packs which again would dramatically reduce the size and weight of the unit. Finally, I would trim unneeded sections of the N64 board down. Particularly the left and right grounding strips which consume a lot of space horizontally.