Turkish Airlines Miles&Smiles - How is TK's OLCI?

Flying next month, with separate tickets (MSP-ORD), connecting to ORD-IST-BEY and back.
I only have about 100 minutes to connect, so I will try to get on an earlier MSP-ORD flight.
If I can't switch connecting flight, how reliable is TK's OLCI? I bought the ticket thru Expedia, and was actually able to retrieve the reservation at thy.com, so I think it should work.
The TK web site says the check-in closes 60 minutes before Int'l flights, but I will already be checked in on OLCI, and not checking a bag.
If I have done OLCI and have my BP in hand, when do I have to appear at the aircraft? At boarding time? I assume they have to do a Document/Passport check somewhere.
Thanks for any firsthand experiences!

Flying out of IST after an international connection you can print your boarding pass online and just go straight to the gate. They will ask to see your passport at the gate but you don't have to go through any other checks as long as your are INT-INT connection.

I don't think you will run into any problems, the only issue I have had at IST airport is in the early mornings the immigration lineup (which you won't have to navigate) are horrible as the day shift agents haven't come on yet and many international flights arrive around the same time in the morning for onward connections.