AMD64/FAQ

Article description::The Gentoo AMD64 Frequently Asked Questions article.

Introduction
This document contains the most commonly asked questions about using Gentoo Linux on systems. Many of these questions come from the forums, IRC, and various mailing lists. The AMD64 Project provides support for Gentoo Linux on this architecture. If you have suggestions or questions about this FAQ, please leave a comment on the associated talk page.

What's the difference between AMD64 and EM64T?
Both refer to 64-bit processors, one from AMD (AMD64) and the other from Intel (EM64T). AMD's 64-bit processors include the Athlon 64, Opteron, Turion, Neo, Phenom, FX, AX/EX/CX, Ryzen and EPYC families. Intel's 64-bit processors include the Core 2, Core iX, Celeron, Xeon, and Pentium (all based on the Core 2 architecture and later). 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 in Gentoo is. As such, AMD64 is a generic reference to 64-bit chips, whether AMD or Intel.

What CFLAGS should I use?
You should use simple CFLAGS to avoid future problems with your system. Supported CFLAGS values are  for both AMD and Intel (EM64T) systems.

What kernel should I use?
You can use almost all kernel sources available in Portage. We recommend using 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.

Will I have a performance upgrade if I use a 64-bit system instead of 32-bit?
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 almost no difference between 64-bit and 32-bit. 64-bit is generally faster when it comes to floating point computing, which is normally the case in multimedia applications and 3D rendering. Linux.com's articles 64-bit performance in Gentoo Linux and 64-bit Linux and BSD are maturing steadily may interest you. There's also a nice thread, Article: 64-bit performance in Gentoo Linux in our forums.

What is multilib and how can I use it?
Every AMD64 processor is able to run 32-bit code as well as 64-bit code. However, when you have a 32-bit application, you are unable to mix it with 64-bit libraries or vice versa. You can, however, natively (without emulation) run 32-bit applications if all shared libraries they need are available as 32-bit objects. You can choose whether you want multilib support or not by selecting the according profile. The default is a multilib-enabled profile.

How do I create a 32-bit chroot?
Please read the 32-bit Chroot Guide.

Can I upgrade from my x86 system to AMD64 by doing emerge -e @world?
Due to several differences between (32-bit) and  (64-bit) installations, it is impossible to upgrade this way. Please perform a fresh install using the AMD64 Handbook.

Note that binary files created on an x86 system most likely cannot be read by packages on an AMD64 system. In particular, some databases, such as OpenLDAP, 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. Database files for MySQL, Berkley DB and SQLite are architecture-independent and can be moved freely when a related daemon, if any, is cleanly shut down.

Will my binary NVIDIA/ATI drivers work?
Yes, NVIDIA and ATI provide drivers that work on AMD64. You can install either or. If you have more questions about these drivers, you should read the nvidia-drivers guide or the ATI FAQ.

How do I use Cool'n'Quiet/PowerNow/SpeedStep features?
You have to compile your kernel with support for these features. You just need to enable the features below:

Then install and edit  with a preferred text editor.

Now you only have to run to make sure it is started every time the system boots.

Can I get Adobe Flash working?
Yes. Install. Be sure to read any messages displayed by the ebuild once it has been emerged.

I want to install package foo, but emerge says: (masked by: ~amd64 keyword)
This means that the package is still in the 'testing' tree. Please read Portage's manual page or the Mixing Software Branches chapter of the AMD64 Handbook for more information.

I want to install package foo, but emerge says: (masked by: missing keyword)
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 (or set of architectures) for the package. The following example shows you can tell Portage to accept the installation of the given package under any keyword.

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.

Where can I get more help or information about Gentoo/AMD64?
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 on chat.freenode.net, Gentoo/AMD64 Forums, or on the  mailing list.