IOS21 was an IOS used by third party games that has an updated STM module. It also contains a copy of the NAND Boot Program in content 1 in some versions, identical to the one in IOS15; this was most likely to apply an urgent patch to the Internet Channel.
Many games such as Wii Sports were also rereleased under this IOS with a newer strap screen, probably in response to TVs getting smashed.
This IOS was used by some versions of DataChk.wad, a factory title, as well as NDEV Menu v1.11.
|Version||Signing bug?||/dev/flash access?||ES_Identify?||STM Release Exploit?||STM IOCTL overflow?||SDI register index bug?||Notes|
|v512[check]||Yes||Yes||Yes||Yes||Yes||Yes||Lowest version released, but not the first release. Supposedly released on Mario & Sonic at the Olympic Games in November 2007. Possibly just a typo for v514 when reporting it.|
|v514||Yes||Yes||Yes||Yes||Yes||Yes||First release; 2.2 update. Most likely forked from IOS19v513, since the KD code comes from there.|
|v515||Yes||Yes||Yes||Yes||Yes||Yes||Added NAND Boot Program, updated Starlet binary|
|v516||Yes||Yes||Yes||Yes||Yes||Yes||Reverted to v514 (new build tag)|
|v517||Yes||Yes||Yes||Yes||Yes||Yes||Added back the NAND Boot Program, and updated the Starlet binary (different from v515 and v516)|
|v522||No||No||No||Yes||Yes||Yes||Standard 3.3rev03 changes. Since this uses an ES module common to all IOSes before IOS37 in this update, the NAND Boot Program is no longer loaded for the Internet Channel, although the NAND Boot Program itself was not removed.|
|?||No||No||No||Yes||Yes||Yes||Only known to exist because content IDs A and B are skipped. Version number is not known.|
|v1295||No||No||No||No||No||No||Only found on vWii and newer RVL-101 units.|
|v26895||No||No||No||No||No||No||Only found on Wii mini|