Some progress: I believe one of the SW4 pins goes to pin R18 under the CPU. According to the Marvell datasheet, R18 cannot be configured as a UART signal. So it looks like SW4 actually is a switch.
My next candidate for a serial port is CN6, which is behind a SATA connector, very much like the jtag+serial header of the LS-XHL
. Pinout is:
+5V (power jack)
Both unidentified signals are routed through internal layers of the PCB and resurface at vias underneath IC7 (a 8-pin serial eeprom). I could not trace them anywhere else.
On other Linkstation PCBs, Buffalo usually interrupt their serial port signals underneath large capacitors. Does anyone think they could have done it underneath an IC this time ? Has anyone desoldered IC7 on a LS-WSXL ?