64bit works on my AMD X2 5600+ with the bootflags "arch=x86_64 -notscverify -force64" just had to revert to chameleon 2 RC4 and no 32bit apps for me yet.

System Software Overview:

System Version: Mac OS X 10.6.5 (10H574)
Kernel Version: Darwin 10.5.0
Boot Volume: 1TB
Boot Mode: Normal
Computer Name: Mac Pro
User Name:
Secure Virtual Memory: Not Enabled
64-bit Kernel and Extensions: Yes
Time since boot: 10 minutes

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GA-Z68XP-UD3: Lion 10.7.3, Windows 7 Professional 64bit SP1 and FreeBSD 9-RELEASE, Core i5 2500K @ 3.3GHz, 16GB 1333 Mhz DDR3 ram(Soon), 1GB GDDR5 Nvidia Geforce GTX 560 Ti, 2X 1TB Samsung F3 SATA HDDs, 1X WDC Blue 500GB HDD; Dell Mini 10v: Obsidian Black, 2GB DDR2 533MHz Ram, 1.6GHz Intel Atom N270, 120GB HDD, 6-Cell, Mac OS X Snow Leopard 10.6.8 Build 10K549