* What does WP solder jumper do?
* Why does the shield use two (same) voltage regulators (but in different packages)? One is not enough for both W5100 and SD?
* The previous version of Ethernet shield had no voltage divisors to do 5V [ch8594] 3.3V conversion on SD_CS, MOSI and SCK card pins, why?
* What is the purpose of 74HC14 inverter added on new version of Ethernet shield? To make sure that when SPI on W5100 is enabled, the chip is put in slave mode? Why do we need to use Schmitt inverter here, not just regular 74HC04 inverter?
* Reference schematics proposes using 0.01µf and 0.1µf bypass caps between GNDA and 3.3VA while the shield uses 10µf (C20) and two 0.1µf (C15, C16) caps instead, why?
* Crystal caps are of different value, 22pf instead of 13pf on reference? Is there an allowed range?
This is a "board stuffing option." You'll notice that the two packages use the same spot on the PCB; you get to pick one or the other depending on price, availability, etc, and the board has pads that will accept either one. Not both.
5V compatible even when operating at lower supply voltage
Another question: can I do voltage divider with 470+220 resistors pair instead of 2.2K+1K? The R1/R2 ratio is very close.
Does the new official shield use only ICSP connector pins to provide SPI interface between Arduino and W5100?
Why 1.8V supply pins are wired up together through a bead although not used?
stack the new revision of Ethernet shield atop Arduino
RESET pin of W5100
do not understand
a lot of open-source hardware projects, suffer from lack of a comprehensive Bill of Materials.. And that's a Bad Thing. Not necessarily Fatal, but Bad (in my opinion).
difference in the level of "badness"