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Many computers today come with support for "hardware virtualization" (called VT-x by Intel and AMD-V by AMD), which improves performance of virtual machines. On Macs, it’s enabled by default, in which case there’s no need to read further! But on PCs (whether running Windows or Linux), it’s not always enabled by default, in which case virtual machines (like the CS50 Appliance) might run unbearably slow. Even with hardware virtualization enabled, though, virtual machines might still feel slow if your computer is a few years old, has a CPU that’s only 1GHz or so, or has only 1GB or so of RAM.

How to Check if Hardware Virtualization is Already Enabled

Windows

  1. Download havdetectiontool.exe from http://www.microsoft.com/download/en/details.aspx?displaylang=en&id=592.

  2. Double-click the file you just downloaded.

  3. If asked whether you want to run this file, click Run.

  4. If asked whether you want to allow the following program to make changes to this computer, click Yes.

  5. If presented with license terms, check I accept the license terms, then click Next.

  6. A window should then report:

    • Hardware-assisted virtualization is not enabled on this computer, in which case you can enable it per the directions below.

    • This computer is configured with hardware-assisted virtualization, in which case hardware virtualization is indeed already enabled.

  7. Select No, I don’t want to send data, then click OK.

Mac OS

Hardware virtualization should be enabled by default on any (Intel-based) Mac manufactured in the past few years!

Linux

It depends on your distribution of Linux. It’s probably easiest to just try to enable it, per the directions below.

How to Enable Hardware Virtualization

Windows, Linux

If your computer supports hardware virtualization, but it’s not enabled, you can likely enable it by changing your computer’s BIOS settings. Generally, you can access those settings by turning on your computer and then immediately hitting F1, F2, F10, F12, DEL, Delete, or Esc, sometimes multiple times (since it’s sometimes difficult to hit the key at just the right time), before Windows or Linux starts to load. Some computers actually mention on the screen at startup which key to press. Assuming you hit the right key, you should then see some sort of "setup" screen, where you might be able to enable "hardware virtualization" or "VT-x" or "AMD-V" or the like; different manufacturers describe the feature differently. Assuming you do find and enable the feature, you’ll generally need to "apply" or "save" your changes, and then reboot. Once Windows or Linux loads, your virtual machines should then run faster (e.g., in VirtualBox).

Below are some representative instructions for some manufacturers' computers (courtesy of Microsoft). Just realize you might need to stray from these instructions on your own computer. And realize that your computer might not even support hardware virtualization!

Dell

  1. Depress the F12 key when boot menu text appears at startup

  2. Select BIOS setup and depress the Enter key

  3. Using the mouse, expand the Virtualization Support menu item by clicking on the plus to the left of Virtualization Support and select Virtualization

  4. Check the Enable Intel Virtualization Technology checkbox

  5. Click Apply

  6. Click Exit

  7. Fully shut down (power off), wait a few seconds, and restart your computer

HP

  1. Depress Esc key when prompted at startup

  2. Depress the F10 key to Configure BIOS

  3. Scroll to System Configuration using the arrow keys

  4. Select Virtualization Technology and depress the Enter key

  5. Select Enabled and depress the Enter key

  6. Depress the F10 key to save and exit

  7. Select Yes and depress the Enter key

  8. Fully shut down (power off), wait a few seconds, and restart your computer

Lenovo

  1. Depress the blue ThinkVantage key when prompted at startup

  2. Depress the F1 key to enter the BIOS setup utility

  3. Using the arrow keys, scroll to Config and depress the Enter key

  4. Scroll to CPU and depress the Enter key

  5. Scroll to Intel® Virtualization Technology and depress the Enter key

  6. Select Enabled and depress the Enter key

  7. Depress Enter key to continue

  8. Depress F10 key to save and exit

  9. Select Yes and depress the Enter key

  10. Fully shut down (power off), wait a few seconds, and restart your computer

Panasonic

  1. Depress the F2 key when boot menu text appears at startup

  2. Select "Advanced" menu in Setup Utility

  3. Change "Intel® Virtualization Technology" setting from "Disable" to "Enable"

  4. Depress F10 to exit Setup Utility

  5. Select "Yes" in confirmation menu

  6. Depress Enter to exit confirmation menu.

Mac OS

Hardware virtualization should be enabled by default on any (Intel-based) Mac manufactured in the past few years!