The below list is from AI, but from a quick view is correct.
Xbox 360 Motherboard Revisions:
• Xenon (2005)
• Zephyr (2007)
• Falcon (2007)
• Opus (2008)
• Elpis (2008)
• Jasper (2008)
• Tonasket (2009)
• Trinity (2010)
• Corona (2011)
• Waitsburg (2012)
• Stingray (2013)
• Winchester (2014)
They are still outputting 720p, but the consoles are good value for kids.