64-bit

[Lutger]

Currently:

LDC is a mature compiler that does linux 64 bit well, but is not available 
for D2, the 'alpha' branch of the language and also doesn't work on windows.

The outdated compiler you speak of would probably be GDC, this project has 
recently been revived. The is no 64-bit dmd yet.

At the moment all efforts I believe are on finishing the D2 language and 
current dmd bugs, as well as a book called 'The D programming language'. 
IIRC the deadline is somewhere end of this year.

What happens after that I don't know, I haven't seen any statement that work 
on 64-bit is planned. I would rather bet on GDC and / or LDC getting full 
64-but support for D2 before dmd.