A quick fact: 32 bit executables can run on 64-bit systems, but 64-bit executables cannot run on 32-bit systems etc.
I though that when the memory got full up the swap file takes the overload. In this event there would be a stutter but not a CTD? - you're right, but the operating system will desperately try to free some memory, and it might close applications on a whim. I know this is the case with Windows 7 (I've actually tested it). Anyways, the system will stutter so much that it'd feel like it's frozen for 10-15 seconds, and then work for a split second and then a new break again....
Clean, and instant CTD's is almost always (99.9% of the time) the result of memory errors, and they never crashes with error messages. Some developers have somehow managed to bypass the limits (Funcom's Age of Conan), with some fancy programming. The memory requirement for games they usually lists, is more a reference to the majority who don't know too much about the computer. It's basically how much memory they expect you to need when you sum up the game plus other programs/services.
Memory isn't the only factor when it comes to stability. It's easy enough to program for consoles because there is only one system. For PC you have so many different hardware combinations (!), and writing bug-free code that works on every combination of hardware, increases the chances for bugs. The real PC testing comes when the game is released, because that is, in reality, you'll probably find almost every bug with a testing team that big! Companies won't hire tens of thousands of testers, they do their best to find and fix the big bugs and let the masses find the rest and then they patch them up. Do you know of a game company who has released a product that's 100% stable on every PC at release without patches?
Thanks for that but what I really meant was this. What is it about Skyrim, which uses an ancient engine, CTD because of memory errors (Oblivion did this as well at first) when other much more modern resourse hungry games do not CTD such as TW2? The large address patch for 64 bit users is surely only papering over the cracks in a fundamentally flawed engine? There is no reason why any game should CTD if it is properly coded and the fact that it is 32 bit is not the issue. Overdo the resourse requirements and you will get lag and stutter but it should not CTD.
On my 32 bit Win 7 system The CTD's have disappeared since I enabled the 3GB switch (possibly placebo because i also installed the latest NVidia Drivers at the same time) but I should not have had to do this as it impacts on performance generally.
In other words I would rather Bathesda sorted out the real problem at source rather than investing unnecessary time on a 64 bit exe so that everyone, XP, Vista, Win 7 , 64 or 32 bit, can benefit.