I'm sure I remember seeing in the aircraft documentation that the 787 portable EFB was actually a hybrid device, with 2 CPUS, 2 sets of memory etc, running both Linux and Windows XP in the same box. The Linux bit was to connect to the aircraft data systems, and the XP part used for driving the display.
This may no longer be accurate as it's been a while since I looked at the documentation, and the systems are changing all the time, but I'm pretty sure it was the case, and given what a strange piece of design it was it was quite memorable. Exactly why it would be this way I'm not sure, probably a way of abstracting the XP bit away from any aircraft systems.
Mechanical standby instruments are always fitted, but sometimes (as in current gen fast jets) can be hidden behind other (movable) readouts to save wasting valuable space - and to be honest if you're in a scenario where you're down to the standbys, you're pretty f**ked anyway, particularly in something like a 787. It takes a ton of failures to knock out *everything* (double databus fail, multiple power bus fail etc.), so anything that takes the cockpit out to that extent would be pretty catastrophic.