In case anyone's missed it in a hundred or so previous threads...

You are NEVER going to get repeatable reliable asynchronous communications at any speed without an xtal or resonator.

You might strike lucky, or you might tear your hair out chasing your tail all because your timing is out of spec.

I've written example code at 300 baud and posted them on this forum in great confidence only to have the code fail for someone somewhere. Async comms is just plain unreliable on internal or RC oscillators.

I have an application which uses a 12F675 (internal Oscillator factory calibrated) which is little more than an Alarm Beeper. It's important to hit the resonant frequency of the Piezo for maximum sound. Now the Piezo is quite tollerant... it likes 4kHz, but is happy from 3.8kHz thru 4.2kHz. Out of every batch of 100 we build, there's always two or three PICs that don't make the grade with the Factory Cal. Now that's a dumb beeper application - and here you want precision async timing with a Factory OSCAL value?