AMD64/FAQ

This is the Gentoo Linux/AMD64 Frequently Asked Questions article.

Introduction
This document contains the most commonly asked questions about using Gentoo Linux on AMD64 systems. Many of these questions come from the [//forums.gentoo.org forums], IRC, and various [//www.gentoo.org/main/en/lists.xml mailing lists]. If you have suggestions or questions about this FAQ, you are welcome to send an e-mail to.

What's the difference between AMD64 and EM64T?
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 Core 2, Core i X, Celeron, Xeon, and Pentium (all based on the Core 2 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 in Gentoo is amd64. As such, AMD64 is a generic reference to 64-bit chips, whether AMD or Intel.

What CFLAGS should I use for AMD64/EM64T?
You should use simple  to avoid future problems with your system. Supported  are   for AMD and Intel (EM64T) systems.

What kernel should I use for AMD64?
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  option activated in the kernel.

Will I have a performance upgrade if I use a 64bit system instead of 32bit?
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.

What is multilib and how can I use it?
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 (without emulation) 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.

How do I create a 32bit chroot?
Please read the 32bit chroot guide.

Can I upgrade from my x86 system to amd64 by doing emerge -e @world?
Due to several differences between an  and an   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.

Can I use Reiser4?
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.

Will my binary NVIDIA/ATI drivers work?
Yes, NVIDIA and ATI provide drivers that work on AMD64. You can install them by executing emerge x11-drivers/nvidia-drivers or emerge x11-drivers/ati-drivers. 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 emerge sys-power/cpufrequtils and edit with a preferred text editor.

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

Can I get Adobe Flash working?
Yes. Emerge. 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 ( man portage ) 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.

How can I help?
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  keyword;
 * Participating in the Arch Testers project;
 * Help answering questions on the mailing lists, forums and IRC channels;
 * Sending patches.

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 , Gentoo/AMD64 Forums, or on the   mailing list.