XO 1.75 A2 ECOs

These are recommended engineering change orders (ECOs) to the A2 prototype of the XO-1.75 laptop. This is NOT a list of changes from A2 to B1, that is located elsewhere.

SD power

These correct a mistake in Embedded Controller pin assignments for the SD power control signals. It has been done to all boards.

• Depopulate R335 and R345 (next to the EC).
• Remove Q16, and short pins 2 and 3 (marked I and O).
• Remove Q21, and short pins 2 and 3 (marked I and O).

VMEM stability

This corrects an undercompensation of the +1.5V memory power supply, and also delays the turn-on of the memory termination power supply. It has been done to all boards.

• Change PR49 to 22K.
• Change PR52 to 47K.
• Populate PC37 with 0.1 uF.

eMMC

This adds a needed pullup to the eMMC CMD signal.

• Populate R95 with a resistor between 4.7K and 10K.

Internal SD Selection

This makes OFW automatically use the internal SD (instead of eMMC) if a card is present in the internal slot.

• Wire the pin of R342 (located on the "top" side underneath the SOC) closest to the WLAN slot to pin 10 of CN21 (the internal SD slot).