32-bit vs 64-bit. What’s the difference?

In short, a 32-bit and 64-bit computer are different in architecture. The main difference lie in the length of data supported by each architecture. A 32-bit machine can only understand data that is 32-bit long. Anything more than that would not be able to read by the machine. Similarly, a 64-bit machine can read data up to 64 bit long. Even though 64 is twice of 32, a 64-bit data can hold much more than double the information of a 32-bit data. This also explains why a 64-bit machine can process and run faster and effectively than a 32-bit machine.

Another difference between 32-bit and 64-bit machine is the amount of memory RAM each can support. For a 32-bit machine, the maximum it can support is only 4GB, whereas for a 64-bit machine, there is theoretically no memory limit cap (or up to 17.2 BILLION gigabytes of system memory). However, most OSes limit to only 16GB (or 32GB) of RAM, which is considered very powerful for today’s desktop computing standard.

What is AMD64?

Instead of using 32-bit and 64-bit, people give them names. A 32-bit architecture is often referred to as i386 or x86 while a 64-bit architecture is widely known as any of the following: AMD64/EM64T/x86-64/x64, depending on the products and the manufacturers.

Why AMD64, you might ask? According to Wikipedia, AMD was the first to come up with the specification of a 64-bit processor. They initially named it x86-64, but later renamed it to AMD64 when they released their first 64-bit processor: AMD-K8 series. Ever since then, AMD64 has become the term for 64-bit processor.

Intel (a competitor of AMD) obviously won’t use AMD64 name for its 64-bit CPU, that why they came up with EM64T, and later renamed it to Intel 64. In some Intel mainboard, during the BIOS bootup, you still can see the word “EM64T” appears in your monitor.

In short, in today technology, AMD64 is now referring to the 64-bit architecture and is not tied with the AMD CPU.

Does AMD64 Ubuntu only works with AMD processor?

Back to the Ubuntu ISO download issue, if you are using a 32-bit computer, you will download the i386 version. If you are using a 64-bit computer, you will download the amd64 version, regardless what brand of CPU you are using.

If you are wondering, a 64-bit computer can run the i386 (32-bit) version of Ubuntu as well. It is just that you are not utilizing your computer to the maximum.

Lastly, don’t bother to run AMD64 Ubuntu on your 32-bit computer. Your system might crash.

Can I run 32-bit applications on 64-bit Ubuntu, and vice-versa?

In usual cases, you can run 32-bit applications on 64-bit Ubuntu, but you won’t be fully utilizing your system. However, the vice versa is not true. You won’t be able to run 64-bit applications on a 32-bit machine (just imagine, you can place a small container into a big container, but you can’t do that the other way round). When installing applications in Synaptic, you might notice that some software comes with the 32-bit and 64 bit version (only shows up when you are using the 64-bit Ubuntu). You can just pick the one you want. Additionally, not all 32-bit applications will work in 64-bit machine, particularly for applications that require access to system hardware settings.

You might wonder why this is a problem. Well, obviously if your system has more than 2GB of RAM, it’d be great to allow your applications or games to make use of it. Furthermore, some applications actually crash when they hit this limit, or start popping up boxes with out of memory errors. If you work on large excel files (500,000 rows+) then you’ll know what I’m talking about.

The Solution

Thankfully, there’s a solution! A great coder by the name of Daniel Pistelli has written a little patching application that will modify your 32-bit programs, and allow them to address up to 4GB of RAM. It’s important to remember that this utility is only useful if you are running a 64-bit OS. If you don’t know what I’m talking about, then here’s an easy way to check:

1. Go to Control Panel, and click view by “small icons” in the top right hand corner
2. Click System
3. As per the image below, next to System Type, it should say 64-bit operating system. If it doesn’t then this utility is of no use to you.

The second thing to remember is that this utility can only be used on 32-bit applications. If you are unsure if an application you are running is 32-bit, run task manager by pressing CTRL-SHIFT-ESCAPE. Click the tab for processes. A list of currently running programs will load. Find your application in the list, and look to see if it has *32 next to it. The example image below illustrates what I mean.

Using the patch

Assuming that you’ve followed the previous two points and now wish to patch your 32-bit application, first backup the executable file of the program you wish to patch. If the patching process fails, or if you need to download an update for the program you are patching, you may need to revert to the original file. Remember, you only need to backup the executable file for the program (i.e. the file with a .exe extension), not the entire program folder itself. Once you’ve done this, download the patching utility from here. Run it, and it will ask you to select your program. Simply select the executable file you wish to patch and the utility will work its magic. Upon completion, it will ask you if you wish to patch another file. If you do, go ahead, if not, quit!

Conclusion

If all goes well, your application should now be able to make use of up to 4GB of RAM. Obviously this will be most useful for resource-intensive applications, and you’ll probably see the greatest benefits with games. Some productivity software will also benefit, assuming you aren’t utilising the 64-bit versions of these (e.g. Excel, Photoshop, 3D Studio Max, and so on.)

The virtual machine window is optimized to work in 32 bit color mode but the virtual display is currently set to 16 bit.

Please open the display properties dialog of the guest OS and select a 32 bit color mode, if it is available, for best possible performance of the virtual video subsystem.

Note. Some operating systems, like OS/2, may actually work in 32 bit mode but report it as 24 bit (16 million colors). You may try to select a different color mode to see if this message disappears or you can simply disable the message now if you are sure the required color mode (32 bit) is not available in the guest OS.

It stated that your system is optimized to work in 32-bit, but the color quality is set to 16-bit. First of all, there is no “display properties” in Ubuntu that allows you to change from 16-bit to 32-bit. Secondly, when you open the monitor option, you can only select 800×600 (or lower) screen resolution.

Here’s what I did to solve the problem.

1. Install Guest Addition. Do not restart after the installation has finished.

2. Open a terminal (in your Ubuntu guest) and type

gksu gedit /etc/X11/xorg.conf

Paste the following to the file.

Section "Screen"
        Identifier    "Default Screen"
        Device        "VirtualBox graphics card"
        Monitor       "Generic Monitor"
        DefaultDepth  24
        SubSection "Display"
                Depth         24
                Modes         "1280x800" "1024x768" "800x600" "640x480"
        EndSubSection
EndSection

Save and close the file.

3. Restart the VM.

It should work now.

Note: This was tested on a Ubuntu Natty 32-bit guest.

Some commercial Linux software, particularly games, only provide 32-bit versions. In these rare cases, you will need to configure your 64-bit machine to run 32-bit software.

Install the 32-bit libraries

Because x86_64 processors are designed over x86 technology, they are still able to support 32-bit programs without any hardware emulation, like what you would need to run x86 programs in a PowerPC or Sparc environment.  In Linux, all you need to do is install the necessary software libraries to run the 32-bit software. Fortunately, many Linux distributions package these libraries for you. In Ubuntu, for example, the package is called ia32-libs. To install it, just open a terminal window and type:

sudo apt-get install ia32-libs

You can also install it graphically from within Synaptic or Kpackagekit on Kubuntu.

Once installed, applications like Skype and games like World of Padman should work without further configuration.

GTK Issues

When running 32-bit programs in a 64-bit environment, Ubuntu still looks for the default GTK engines. This will cause you to receive an error such as this: “wrong ELF class”. This type of error can be particularly annoying in applications like Chromium, the new open source version of the Google Chrome browser.

Ubuntu does actually install the default 32-bit version of the GTK engines in /usr/lib32/gtk-2.0, but what I discovered in my case was that GTK themes like the one I was using, qtcurve, were not found in this directory.  The result was really ugly GTK programs.

The quick solution was to do the following:

1. Find the 32-bit package of the theme you are using.  In my case, I searched ubuntu packages.

2. Download the package and extract its contents like you would a normal compressed file.

3. Find the library file for the theme. For qtcurve it was found at ~/download-directory/usr/lib/gtk-2.0/2.10.0/engines/libqtcurve.so.

4. Copy the library to the lib32 directory:

sudo cp ~/download-directory/usr/lib/gtk-2.0/2.10.0/engines/libqtcurve.so /usr/lib32/gtk-2.0/2.10.0/engines/

For Chromium this was all that was required because the Chromium startup script was already configured to look in /usr/lib32/gtk-2.0. If the startup script of the program you are running does not look there but instead looks to /usr/lib/gtk-2.0, you will need to modify the startup script or export an environment variable before starting it by opening a terminal window and typing:

export GTK_PATH=/usr/lib32/gtk-2.0
command-to-start-app

If there is no startup script for the program, you could create one with the above environment variable set.

If All Else Fails

I have found some applications, such as Boxee, refuse to behave nicely in a 64-bit environment under any normal circumstances, even with ia32-libs installed. The only viable alternative besides chucking your 64-bit machine or chucking the software is to run it in a chroot environment. This literally installs an entire 32-bit version of your operating system within a directory on your computer. It will take more space than simply installing a few libraries, but it ensures that all of the 32-bit components, including 3D graphics kernel modules, are installed.

You can read a guide to setting up a 32-bit chroot on Ubuntu Forums.