OpenBSD/amd64 runs on AMD's Athlon-64 family of processors in 64-bit mode. Note that OpenBSD/i386 also runs on these processors, but in 32-bit mode.
It can be expected to install and run with minimal difficulty on most current hardware.
A few problems exist with the bootblocks, kvm libraries, and some floating point operations. Obviously this is fairly new, so it will take time to find other issues and fix them.
Snapshots are made available from time to time, in this location as well as in a few mirrors. Here are the OpenBSD/amd64 snapshot installation instructions as well.
There are several installation media provided:
Booting off the CD provides an El Torito 2.88MB floppy image
that contains almost all OpenBSD drivers.
This also includes minimal USB support (storage devices and keyboard).
For the latest list of drivers available on this image, take a look at the
RAMDISK_CD
kernel configuration file.
This 1.44MB floppy image contains the most common drivers.
It is designed to cover the most typical PC. As a general rule, you will
find that the missing drivers are ones which need large microcodes to run,
such as for rare scsi cards, gigabit ethernet cards, or RAID devices.
For the latest list of drivers available on this image, take a look at the
RAMDISK
kernel configuration file.