Members of the Atariage forum have put together a “Community Build” of the Stella Atari emulator that can be installed onto the Retron 77: http://atariage.com/forums/topic/281462-retron-77-community-build-image/
This image should be loaded on a MicroSD card using a disk image software, the same way a RaspberryPi image is loaded. Reports have shown that it increases performance, however as far as I know, no one has posted any measurable lag tests. If nothing else, the build is shown to increase compatibility, so it may be worth updating for any Retron 77 owners: http://atariage.com/forums/topic/280100-retron77-compatibility-list/
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#retron77, #atari2600