Allwinner announced A20 processor as drop-in replacement for A10 designs, i.e. you could re-use your A10 board design for the new A20 processors which offer dual core power.
We already blogged that we got preliminary info and schematic to evaluate and last two days our developers were busy to compare the schematic info (as there is no datasheet for A20 yet).
Most of the GPIO ports on A20 match A10 ports, just some ports in A20 now have more functions but keep the old port functionality as well.
Well done Allwinner!
We spot some balls that are with differnt functionality though:
ball.A19 A20.TWI4_CLK A10.GPS_MAG ball.A20 A20.TWI3_CLK A10.GPS_CLK ball.B20 A20.TWI3_SDA A10.GPS_SIGN
these three are minor changes, we do not use GPS signals on board and they go to GPIO connector so no problem
another difference is on these two balls:
ball.R14 A20.NC A10.VREGIO_HDMI ball.R16 A20.NC A10.PLLREGIO
these two balls are left not connected on our A10 design too, so no problem
there are some differences in the PIO power supply:
ball.H10 A20 connected to 3V A10 connected to 3.3V ball.J10 A20 connected to 3V A10 connected to 3.3V
these two balls are connected to 3V in A20 schematic and to 3.3V to A10 schematic, we have to investigate this further!
the major differences between A10 and A20 are in the DDR3 wiring:
ball.N3 A20.SCKE A10.SCKE0 ball.J3 A20.SCK1# A10.ODT1 ball.J4 A20.SCK1 A10.SCKE1 ball.AA4 A20.A15 A10.SCS1
A10 have two chip-select one clock and two clock enables (second is not used in our schematic) and addresses up to A14
A20 have one clock enable with two pairs of clocks (one not wired on the A20 reference schematic) and addresses up to A15
so both chips can address up to 2GB RAM but in different way.
We didn’t complete our A10 schematic this info comes right on time, so we can make our schematic compatible with both A10 and A20 and to may support up to 2GB RAM
Conclusion: YES, it’s possible to design board which to may work with both A10 and A20, but not if you have not received the A20 info when you made your A10 board :)