It wasn't quite as simple as just RS485 buffers, but that's on the right track. All the lines MUST be buffered if they are to go outside the box, and also need filtering for both radiated and received EMI, as well as spike protection. A number of lines go directly to the SA1100, which doesn't cope well with spikes or signals over 3.3V.

The pinout of the connector on the motherboard is:

Pin 1: LCD bus bit 0 (unbuffered, 100R series resistor)
Pin 2: GND
Pin 3: Pixel clock (unbuffered, 100R series resistor)
Pin 4: GND
Pin 5: Line clock (unbuffered)
Pin 6: Control line to PIC
Pin 7: Frame clock ((unbuffered)
Pin 8: GND
Pin 9: LCD BIAS signal (used to generate heater voltage for VFD)
Pin 10: IR RX line from CIR unit
Pin 11: IRDA RX line
Pin 12: GND
Pin 13: IRDA TX line
Pin 14: VCC3 (fused 1A)
Pin 15: VCC3 (fused 1A)
Pin 16: VCC5 (fused 1A)
Pin 17: VCC5 (fused 1A)
Pin 18: GND
Pin 19: DC IN (fused 1A, pulled to GND via 12K)
Pin 20: DC IN (fused 1A, pulled to GND via 12K)

Note that if you get it wrong, ie 5V or DC IN shorted to any signal lines, you WILL kill the SA1100, and possibly nuke other components as well. The same may well apply if the power rails are shorted together.

It's certainly possible to extend the cable if it's done right. My board set was designed for a 3M extension, and has been tested with a 100M cable successfully

pca