Here is what Milan Babuskov wrote about his experience with Linux Slackware and Firebird related packages on x64 system :
I just installed Slamd64 version 12.2. I know that Slackware -current is 64bit and Slackware 13.0 is out, but out-of-the-box 32bit compatibility of Slamd64 is very tempting, so this is the first 64bit slackware I installed.
Install went fine, and KDE is running in a matter of seconds. Now, time to compile all the needed stuff for development. Basically, all I need is Firebird, FlameRobin and PHP extension for Firebird (i.e. InterBase).
Michael uploaded a setup for Windows XP 64 and Vista 64, could those of
you using one of those systems please try it and report success or failure?
It works on my machine, FWIW…