Were written from secure stand point?
None, as far as I have seen. If the software *IS* written properly and reviewed properly and QA'd properly, it shouldn't matter *WHAT* hardware it is on.
IOW [link|http://en.wikipedia.org/wiki/Kerckhoffs'_principle|Kerckhoffs' Principle] (yes I know, its wikipedia) applies here. Even though its not really and truly about cryptography, the lessons still apply.
Since corporations producing these voting machines are all about profit and nothing else... They ignore Kerckhoffs' Principle, citing costs, not enough TIME, deadlines... whatever. If they are not held to the fire, they won't do it, ever!
So, what to do. Force the corporations to prove it or develop this way. How? I don't quite know, but its the only thing that can make this problem go away.
Maybe treating this problem like NASA does with software problems related to mission critical stuff, will "cure" the endemic issues.
When I just typed mission critical, I don't mean "Corporate Mission Critical", I mean "OH NO! The crew just died" or "Umm, the vehicle just blew up" or "Hey! All the oxygen is being vented into space" mission critical stuff. These issues need to be treated similarly.