Diablo is the codename for the OS2008 Feature Upgrade (corresponding to Maemo 4.1), released in June 2008. Major features include significant improvements to the built-in Application manager, incremental operating system upgrades without reflashing ("Seamless Software Update", SSU), Modest as the default mail client, and a new version of the MicroB browser with better performance and some interface improvements (though still based on the same Gecko release as Chinook's MicroB). Diablo also included an implementation of the WiMAX stack for the short-lived N810 variation called N810 WiMAX edition.