Sonnet Technologies on Monday unveiled their latest upgrade: the Encore/ST G4 Duet 1.3GHz. This dual processor upgrade is compatible with most Power Mac G4 systems in the “Sawtooth” series, including the AGP Graphics, Gigabit Ethernet, Digital Audio and Quicksilver (2001 and 2002) models. Its processors will run at 1.267GHz in the Digital Audio and Quicksilver machines, and it’s not compatible with an early version of the AGP Graphics G4 (see Sonnet’s Web site for more information ). The new upgrade will be available in June for US$699.95. OS compatibility includes Mac OS 9.2 through Mac OS X v.10.3.3.