I believe it was some MediaTek demo code that could run directly on the modem for a 1-chip GSM featurephone or in a AP+BP 2-chip 3G configuration. Wasn't Symbia

I believe it was some MediaTek demo code that could run directly on the modem for a 1-chip GSM featurephone or in a AP+BP 2-chip 3G configuration. Wasn't Symbian, nor CE nor Linux, more like a giant Arduino sketch. There were a lot more giant Arduino sketches / baremetal library-based big main loop RTOS in the '00s.