Both refer to 64-bit processors from AMD (AMD64) and Intel (EM64T). AMD's 64-bit processors include the Athlon 64, Turion, Neo, Phenom, and Opteron families. Intel's 64-bit processors include the Core2, Core iX, Celeron, Xeon, and Pentium (all based on the Core2 architecture). The last few versions of the old Pentium 4 and Xeon chips also support EM64T.

The AMD line of 64-bit processors were released well ahead of Intel's offering. Therefore, for historical reasons the arch keyword for all x86-64 compatible architectures is amd64. As such, AMD64 is a generic reference to 64-bit chips, whether AMD or Intel.

You should use simple CFLAGS to avoid future problems with your system. Supported CFLAGS are -O2 -march=native -pipe for AMD and Intel (EM64T) systems.

You can use almost all kernel sources available in Portage. We recommend using gentoo-sources because it is a special kernel designed for Gentoo Linux. It contains lots of AMD64-specific patches and therefore is the only kernel officially supported by Gentoo/AMD64.

Make sure you have the IA32_EMULATION option activated in the kernel.

# cd /usr/src/linux
# make menuconfig

Executable file formats / Emulations  --->
  [*] IA32 Emulation

That is a difficult question to answer. In some cases, you will experience a performance improvement, in other cases you will not. For everyday use, there is nearly no difference between 64bit and 32bit. 64bit is generally faster when it comes to floating point computing which is normally the case in multimedia applications and 3D rendering. This article (and a related article) may interest you. There's also a nice thread in our forums.

Every AMD64 processor is able to run 32bit code as well as 64bit code. However, when you have a 32bit application, you are unable to mix it with 64bit libraries or vice versa. You can, however, natively run 32bit applications if all shared libraries it needs are available as 32bit objects. You can choose whether you want multilib support or not by selecting the according profile. The default is a multilib-enabled profile.

Please read the 32bit chroot guide.

Due to several differences between an x86 and an amd64 installation, it is impossible to upgrade. Please perform a fresh install. The installation is slightly different than an x86 one, so please use the AMD64 Handbook.

Also, binary files created on an x86 system most likely cannot be read by packages on an amd64 system. In particular, databases such as MySQL, innoDB, Berkeley DB, SQLite, OpenLDAP, etc. cannot simply be copied as-is. You will need to dump the database into an architecture-independent format, such as a text file, before attempting to restore it on an amd64 system.

Reiser4 is not available from any kernel offered by the Gentoo Kernel project, thus the AMD64 team doesn't support it. The answer is no.

Yes, NVIDIA and ATI provide drivers that work on AMD64. You can install them by executing emerge nvidia-drivers or emerge ati-drivers. If you have more questions about these drivers, you should read the Nvidia guide or the ATI FAQ.

You have to compile your kernel with support for these features. You just need to enable the features below:

Power management options --->
  [*] Run-time PM core functionality
  [*] ACPI (Advanced Configuration and Power Interface) Support --->
    <*>   Processor
    <*>     Thermal Zone
  CPU Frequency scaling --->
  [*] CPU Frequency scaling
         Default CPUFreq governor (ondemand) --->
  -*-   'performance' governor
  <*>   'userspace' governor for userspace frequency scaling
  -*-   'ondemand' cpufreq policy governor
  <*>   ACPI Processor P-States driver
  <*>   AMD Opteron/Athlon64 PowerNow!
-*- CPU idle PM support

Then emerge cpufrequtils and edit /etc/conf.d/cpufrequtils with your favorite editor.

# Options when starting cpufreq (given to the 'cpufreq-set' program)
START_OPTS="--governor ondemand"

# Options when stopping cpufreq (given to the 'cpufreq-set' program)
STOP_OPTS="--governor performance"

Now you only have to run rc-update add cpufrequtils boot to make sure it is started every time you boot.

Yes. Just emerge adobe-flash. Be sure to read any messages displayed by the ebuild once it has been emerged.

This means that the package is still in the 'testing' tree. Please read man portage or the Mixing Software Branches chapter of the AMD64 Handbook for more information.

This means that the package has not been tested yet. It does not necessarily mean that the package does not work. You can unmask it by accepting another architecture for the package. The following example shows you can tell Portage to accept any keyword for a given package.

# echo "category/packagename **" >> /etc/portage/package.accept_keywords
# emerge packagename

If it works fine for you, please let us know and file a bug on Gentoo's Bugzilla, so that the AMD64 team can keyword the package and other users can benefit from your test.

With a growing popularity of the amd64 architecture, we also increasingly need more help. There's still much work to be done to improve the quality of Gentoo/AMD64. An average user can help us by:

• Filing general bug reports
• Testing software that does not yet have the ~amd64 keyword
• Participating in the Arch Testers project
• Help answering questions on the mailing lists, forums and IRC channels
• Sending patches

If any of your questions wasn't answered here, you can try other resources listed on our project homepage. You can also ask us at #gentoo-amd64 on irc.freenode.net, Gentoo/AMD64 Forums, or on the gentoo-amd64@lists.gentoo.org mailing list.