Intel is pleased to announce the BIOS Implementation Test Suite (BITS), a bootable pre-OS environment for testing BIOSes and in particular their initialization of Intel processors, hardware, and technologies. BITS can verify your BIOS against many Intel recommendations. In addition, BITS includes Intel's official reference code as provided to BIOS, which you can use to override your BIOS's hardware initialization with a known-good configuration, and then boot an OS.

BITS functionality fits in three broad categories:

  • Testing: run test suites to check how the BIOS configured your platform hardware.
  • Configuration: override the BIOS hardware configuration using a known-good configuration, such as by running Intel reference code
  • Exploration: experimental tools and information gathering

BITS consists of a modified GRUB2 bootloader, with many additional commands to probe and manipulate hardware configuration, as well as scripts using these commands to test and reconfigure hardware. GRUB2 already provided a very capable pre-OS runtime environment, including many features commonly found in standard libraries, as well as a scripting language, command line, and menu system; thanks to the GRUB2 developers for the great platform to build on.

To support the functionality we needed in BITS, we added:

  • Support for initializing and running code on all CPUs in an SMP system.

  • Many new commands for manipulating hardware resources such as model-specific registers (MSRs), CPUID, PCI and PCI Express devices, and memory addresses; in all cases these operations occur from a designated CPU, allowing access to CPU-specific resources and asymmetrically mapped system resources.

  • Many new commands supporting the hardware configuration and BIOS test-suite infrastructure, including a full C expression evaluator for integer values (so you don't have to resort to implementing more commands in C just to shift, mask, and otherwise twiddle bits).

In addition to those changes to GRUB2 itself, BITS includes configuration files which build a menu exposing the various BITS functionality, including the test suites, hardware configuration, and exploratory tools. These scripts detect your system's CPU, and provide menu entries for all the available functionality on your hardware platform. You can also access all of the new commands we've added directly via the command line.

The current version of BITS focuses primarily on CPU configuration and power management. It includes extensive support for IntelĀ® processors based on the microarchitecture code name Nehalem and newer, which includes Intel Core i7, i5, and i3 desktop and mobile processors, and corresponding Intel Xeon server processors.

Some examples of what you can currently do with BITS:

  • Detect if your BIOS properly configures processor power management.

  • Run Intel's power management reference code to override your BIOS's configuration. This includes writing the ACPI tables for P-states and C-states, replacing those normally provided by your BIOS. In particular, you can even turn off power management in your BIOS entirely, use BITS to initialize it, and then chainload Linux and run powertop to see full P-state and C-state support via cpufreq and cpuidle.

  • Detect the frequency and duration of BIOS System Management Interrupts. This tool shows the average duration of SMIs (grouped by orders of magnitude), the time between a few SMIs in each group, and the worst-case latency observed.

  • Check how long a CPU core and the entire processor package spend in C-states (sleep states), by directly checking the CPU's residency counters (when available on your platform). You can compare this C-state residency measured in a pre-OS environment to what you observe under Linux, to help attribute unexpectedly low C-state residency between Linux background tasks or configuration and BIOS configuration.

For more examples of using BITS, see the screenshots page at

Many pieces of functionality implemented in BITS demonstrate the use of newly disclosed and documented hardware information, now provided in the Intel 64 and IA-32 Architectures Software Developer's Manuals (SDM).

You can get BITS from the BITS homepage at We appreciate any feedback you might have on BITS, including questions, comments, bug reports, feature requests, or patches. In particular, the BITS infrastructure makes it possible to implement a wide variety of tests via simple text configuration files, and perform experimentation directly on the GRUB command line; give it a try and let us know what you think!