The region specific information about the Nintendo 64 isn't very clearly published. Some of this information has simply been lost to the ages (i.e. dead or outdated websites), also the original console release was before what most people consider the "Internet Age".
I will be very clear my information for US and Japan are both from research and hands on experience. My experience with Europe/Australia i.e. PAL is limited to research only.
Everybody loves a chart so lets start there. Follow the links to sections below for more details.
The US and Japan versions of the console are nearly interchangeable, the only "region" locking is a physical notch in the cartridge with a matching peg in the console.
Region Mod Technique list available here: Do these at your own risk, none are supported by me or Nintendo.
US games in Japanese consoles and Japanese games in US Consoles should work just fine after either the console or cartridges are modified to fit.
PAL Cartridges use the same notch position as the Japanese cartridges. When using a modified US/Japanese console with a PAL game cartridge may cause problems. These problems should not cause any permanent damage but possible side effects include.
This is the 4 MB (Megabyte) RAM Memory Expansion PAK that some games required and others may use if available. This is a highly recommended accessory for any N64 console!
This item has no known region / language / technical limitations. It's either 1 or 2 Memory IC's there is no logic to restrict how it works. The connector and installation method are identical across all regions.
The standard controller assumes either a Nintendo or 3rd party Tri-Wing controller. These controllers respond to the standard console request with the same response data.
Nintendo branded controllers had some issues with the Joysticks wearing out to the point they would not "self center". While 3rd party controllers may use a different joystick that doesn't have that problem it could still be a poor quality or an inaccurate joystick.
NOTE: Some 3rd Party controllers DON'T support the accessory port in the controller, to the point of completely blocking it! This applies especially to those intended for PC use with USB.
The Rumble PAK request and response data is not region specific.
Nintendo branded Rumble PAK's always use 2 AAA batteries. The amount of power that is available to each controller is limited so this is a very safe approach.
Third party Rumble PAK's may try to use the power available from the console. This might work for one player, but multiple players with these Rumble PAK's may cause problems for example console may hang or reset while playing.
Nintendo always referred to this accessory as the Controller PAK, most users recognize it for what it is and refer to it as the Memory PAK.
The Controller PAK has some considerations for use across regions. This is easier to explain in steps:
This same issue would apply to any European games where the game name includes non-ASCII characters.
These memory units are small with a maximum of 16 save games, I would recommend purchasing one or more Controller PAK's for each region. For example one for Japanese games, one for Europe, another for Australia, and one for North America.
There is at least one site that states that the Transfer PAK is not region locked (i.e. Japan Transfer PAK can be used with a US game/console combination.
I have tested the following combinations:
Note: The GameBoy / GameBoy Color games were not region locked.
Any N64 games that use the Transfer PAK to read Gameboy games could make their own determination of what Gameboy games they would support. For example a US N64 game developer could decide to support all regional versions of their Gameboy game and determine which features in their game would be enabled, maybe unlocking different characters for each regional version of the gameboy game.
The Voice Recognition unit is a language locked device, the US VRU only works with the English language and the Japanese VRS only works with Japanese.
The simple answer here is that the console region doesn't matter. Cartridge and Voice Recognition unit must match.
Good: Japan Game Cartridge, North American Console, Japanese VRS.
Good: North American Cartridge, Japan Console, North American VRU.
I don't believe a Voice Recognition unit was released for Europe or Australia.
The 64DD had sales of 34,962* (or higher) which is pretty limited for a Nintendo product, even the Virtual Boy sold approximately 500,000. There were only 11 games/programs released for the 64DD all in Japan. I have verified a 64DD with a North America Console works fully, although everything I've seen is in Japanese. I'm sure it would not work with a PAL console, but that would probably be a software and CIC compatibility issue.
*Reference: 64DD Serial Numbers "registry".
Expected behavior 64DD Attached to console (i.e. 64DD Troubleshooting) :
Notes:
Not region locked, but has limited usage outside of it's primary market of Japan.
The Mouse is probably one of the more interesting accessories. It was intended for use with the Mario Artist series that was only released on the 64DD in Japan and used to good effect in all (Paint, Talent, Communication, Polygon Studio) of those titles. It has been reported to work with several North America released games including Starcraft, Goldeneye and Perfect Dark. The gamers that have tried this usage don't claim it's good but the fact that it works is pretty cool.
Not region locked, but not very usable in any region. It supports the standard ASCII character set as well as Japanese characters. Only the Japan RandNET internet access 64DD cartridge supported it.
Not region locked, but only usable with one Japanese game.
This controller isn't usable as a normal controller, it's technically very different.
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