CAT-DEV
The CAT-DEV (Cafe Tool for Development; Product Code: WUT-001) was the main development system for the Wii-U. It can come in black, white, red (internal units only), yellow (internal units only), or beige/tan/gold colors in a rectangular box. Most CAT-DEV's will be 'beige' which is most commonly used for the later and final revisions of the CAT-DEV.
Each CAT-DEV includes the normal Wii-U hardware (minus the disc drive) with an additional 2Gbs of Ram (bringing the system to 4 Gbs total), as well as an extra board called a "Host Bridge" that handles numerous activities such as Debugging, Optical Disc Emulation, and Host I/O Communication. There are two known variants of the Host Bridge, the 'Toucan', and the 'MION'. Any CAT-DEV that has a MION host-bridge will have an internal HDD. It is not currently known if previous models (i.e. Toucan's) have internal HDDs. CAT-DEV's with a Toucan host bridge will feature a physical serial port, while MIONs will use a USB Serial adapter. MIONs will also have a three additional Wired RF serial ports, and a port for LAN.
CAT-DEV's can come configured in multiple boot modes. Although the boot modes are slightly different based on the revision the modes effectively fall into three categories: the default mode where loading is controlled from a connected host pc, a 'reader' mode where data is loaded from internal memory/hard drives, and a mode where it can request from the host but fallback. See more info on the boot modes below.
The typical development flow for a MION CAT-DEV is to plug it into the network, and run "cafeon", or "caferun" from the Cafe SDK to emulate a full filesystem on the host PC. Developers could add, and remove directories dynamically to add titles and directories. Debug output is usually streamed over the network connection, but can also be gathered over a USB-Serial connection.
Known Versions
There are a total of 6 'official' revisions of the CAT-DEV, and at least 2 'unofficial' revisions. Because there are so many versions, and most of the time the functionality does not change from a developer perspective, it is generally easier to refer to CAT-DEV's by their "Host Bridge". As most of the functionality is tied to a particular Host Bridge.
Use the tabs below to navigate through the various versions of CAT-Dev, grouped by their Host Bridge.
There are a few very early models which do not have any host bridge at all. These models are so early, that we do not know much about how they worked.
- Wii U Boards: CAT_CPU_X1
Internal evaluation board that was used inbetween Cortado, and V0. ARM Security had not yet been enabled. JTAG is present.
- Wii U Boards: CAT_CPU8_X2
Internal evaluation board that came before V1, most notably ARM Security had not been enabled on this board. JTAG is present.
Internal board that came before any bridging. This is the first board that had enabled ARM Security.
Toucan is the name of the host-bridge for the CAT-DEV v2. Although one Toucan was sold on eBay, and we have log messages from various components; very little is known about them. TOUCANs still booted with with disc images similar to a NDEV. However, the TOUCAN itself started doing slightly more handling a custom SDIO protocol. Hence in some places the TOUCAN was called the "SDIO Bridge". It also had very similar set of USB ports to the NDEV, one for debugging, no lan port, and behavior from the SDK.
It is believed all Toucans are black in color, and it is known that all versions do not have a LAN port on the front.
(~early-mid 2011, Latte A2X?)
- Wii U Boards: CAT_CPU8_X4
first unit to come bundled with a DRC, one known system sold on ebay, where the below pictures from from, last system without an ethernet port. (unknown SDK support)
MIONs are the most well known Host Bridge because they were the most widely distributed, and all known variants community members have are MIONs. The MION Host-Bridge has an internal HDD, firmware, FPGA firmware, and contains the LAN port for communicating with a Host PC over the network. MIONs also introduced numerous network protocols to communicate with the host pc and load files from the host pc over the network. The only confirmed board variant that we have pictures of is: "CATHDD-X5" (present in MP2 units, and at least one V4 unit).
You can find more information about the host bridge MION board down below.
- Wii U Boards: CAT_CPU8_X5
(July 2011, Latte A3X?)
White-cased unit that was only supported for a very short time (CafeSDK 2.0.0-2.0.4). Appears to share a case with V4, but can be distinguished from it by the acceptance dates listed on the top sticker.
- Wii U Boards WUP_DEV_X6
Officially Supported for CafeSDK 2.0.0.0-2.09.22.0
While it's common for a CAT-DEV v4 to be confused with a CAT-DEV v3 (sometimes it's even been improperly labeled on various sites), it is it's own distinct unit. The internal release notes for the differences between a V3, and V4 are:
- "Increased Operating frequency of the CPU by 25%"
- "The speed for writing to memory when using locked-cache DMA is the same as final."
- "Speed of transfer from MEM1 to MEM2 is final."
- "L2 Cache Fetch doubled when using lock-cached DMA"
In general these are effectively near final units, and some were even used for development/testing until the end of the Wii-U's lifecycle.
(?, Latte A5X?)
Not much is known about the MP1 Units.
(?-Final, Latte A5X)
Final revision supported from CafeSDK 2.0.0-Latest.
The following Wii-U boards are known to be present in a CAT-DEV MP2:
- WUP-DEV-X8 - WUP-DEV-X9 - WUP-DEV-X10
The following consoles don't fit into one of the above categories, and very little is known about them.
IOSU has support for talking to a CAT-DEV that has a Latte B1X chip inside of it. It's not clear if they were ever distributed externally, or used internally.
EV variant which was introduced with Latte A5X/CAT-DEV MP2.
"Internal" Units
In July of 2026 4 CAT-DEV units were sold that were Bright Yellow, and Red which were not described previously in any documentation.
-
Internal CAT-DEV units from a top view. -
Internal CAT-DEV units from underneath. -
Internal CAT-DEV units underneath but from a more top cenetered view. -
Internal CAT-DEV units all packed in a package.
It turns out these units came from either within a factory, or directly from Nintendo themselves. It is currently unclear which source they came from, but these are definitely internal units as they contain an extra board called the "CAT-JTAG".
This extra CAT-JTAG board (pictured in the bottom left in the photo above), is a board that would never have been sent to any developers. It is not currently known if this is JTAG for the underlying PowerPC CPU "Espresso", or the ARM CPU "Starbuck".
Interestingly the yellow units all were labeled "V4W" in their serial:
-
CAT-DEV Yellow unit Serial label for the unit: "S/N: CAT-DEV-V4W1953" -
CAT-DEV Yellow unit Serial label for the unit: "S/N: CAT-DEV-V4W1788" -
CAT-DEV Yellow unit Serial label for the unit: "S/N: CAT-DEV-V4W1740"
This is the exact same serial number format that CAT-DEV v4 Units that were sent to other developers. Which implies these yellow units have the exact same features of the white V4 units that external developers got (just with the extra CAT-JTAG board). The red CAT-DEV unit did have a different serial number format "V4ES":
Investigation of this unit is still continuing, but it is speculated this might of been a bring up unit in the factory to aid in testing 5GHz wireless as it had an extra 5Ghz wireless module that was sold with it.
Serial Port Settings
Although later CAT-DEV models do not have a dedicated serial port, they do have support for accessing a serial like console through a Telnet connection on the TCP port 6008, or by using a USB Serial Adapter. The only ones called out as specifically supported in the Cafe SDK docs were:
- US232B/LC
- VSCOM / USB to RS-232 Cable / FTDI FT232B
- QVS / USB to RS-232 Cable / FTDI FT232B
If you connected through this serial USB connection, you would need to configure your application (such as tera term) to read with the following settings:
- Baud Rate: 57600 - Line Endings: CR/LF
ODD Connection
Although CAT-DEV's do not normally come with a disc drive in anyway, they do support having a disc drive attached. It is doubtful anyone outside of Nintendo used this, as it requires voiding the warranty of the device. To do so, open the unit, and connect the ODD's SATA device connector to the Host Bridge's sata strip. Next set PCFS over Sata to "disable", and you can use the unit & disc drive like normal.
MION Board
The CAT-DEV's from V3 onwards started featuring a "MION" board as the 'host bridge' (short for "Multi I/O Network") that contained the internal hdd, as well as is the device that managed the LAN port connection. It is the real brains of driving the power, serial output, and filesystem (in certain boot modes) for the CAT-DEV. When developers are interacting with the CAT-DEV through tools in the SDK like "cafeon", "findbridges", etc. They're actually interacting with the MION board directly. There are three boot modes available on MION CAT-DEVs: "PCFS", "DUAL", and "HDD Reader Mode". HDD Reader Mode is the only mode that allows the actual Cafe OS, and "wii-u" portion to boot when first receiving power. In "PCFS", or "DUAL" mode the MION will not power on the actual Cafe OS until a HTTP Request is received to power on the underlying OS. In many cases you must also spin up several TCP, and UDP services for the device to interact with, but every known MION has a series of flags you can set to force booting when 'PCFS' is turned on. MIONs are also how developers would 'find' the cat-dev on a network since there was no visual indicators when first powering them on. They did this through UDP Broadcast packets on port 7974. They also have support for fetching the internal memory, and disk state (although only 512 bytes at a time).
One of the services exposed by the MION is telnet, which requires a username, and password. The username is "mion", and the password is: "/Multi_I/O_Network/" (this username/password can also be used on the web interface). Although the telnet doesn't seem to expose anything incredibly useful, it is possible to get logs from the MION board itself, as opposed to the logs coming from CafeOS. This username/password is consistent across all known versions of MION Firmwares, and seems to be added on every boot even if it's removed.
The MION boards have the following known firmware versions:
| MION FW Version | SDK Release | Released At | Notes |
|---|---|---|---|
| 0.00.12.29 | |||
| 0.00.13.58 | |||
| 0.00.13.74 | |||
| 0.00.13.88 | Does not have support for 'bypassing' PCFS boot by telling the machine to boot without giving it a PCFS configuration. It still attempts to boot with PCFS configured. | ||
| 0.00.14.70 | |||
| 0.00.14.77 | Introduced "power_on_v2" HTTP API, and the ability to take control over someone else's MION, and added proper support for overriding booting out of PCFS when PCFS is enabled. | ||
| 0.00.14.80 | 2.12.13 |
DRC2 (second GamePad port)
The v3 CAT-DEV is known to have had a second DRC port covered up with semi-transparent plastic. This could indicate a feature which was only included on internal/special order units and was being covered up for mass release, similarly to wired WiFi on the NDEV, or that they were undecided about supporting 2 GamePads. It was added in later Cat-DEV's (MP2 units are known to have them).
