На C839 и ногу C5 контроллера D600. С этой стороны больше некуда.

Добавлю. На этих точках присутствует VRTC.
Из того же мануала:
VRTC is used to supply the RTC block in MARTHA. The regulator for this
voltage is always powered up when a battery is connected and cannot be
switched off.
RTC (REAL TIME CLOCK )
The real time clock is a part of the MARTHA chip. A 32.768 kHz crystal is
placed close to the inputs on MARTHA. A separate voltage, VRTC, which is
generated by a regulator in VICTORIA 2+, powers the RTC block in
MARTHA.