I understand that originally there was a triennial Torah reading common in Israel and an annual one common in Babylon. Most people now use the annual custom. (Note that the triennial reading that is common in Reform and many Conservative shuls is actually the same as the annual reading but divided into "thirds". It does not resemble the original sequential triennial reading of old.)
When where these organized and who did them? Are the sidrot (weekly readings) that we have currently the same as the original ones (i.e. their starting & ending locations? I'm not concerned about which sidrot were decided for doubling - there's a different reasoning for that. I am also aware that the names of the sidrot changed.) If not, what was changed and why?