Windows 8 build 7973 (fbl core2 sid data)

Windows 8 build 7973 (fbl_core2_sid_data) is a Milestone 3 build of Windows 8. The x64 checked/debug compile of this build was uploaded to BetaArchive on 19 September 2015, while the x86 free compile was uploaded on 5 June 2022.

Changes

 * There are massive updates to the Metro OOBE:
 * The flower background has been replaced by a single color with a spotlight in the middle.
 * "Express settings" debuted as "Recommended settings".
 * Options and buttons have been uplifted to better fit with the Metro design.
 * This marks the first time where the new loading spinner is used. It can be seen at the end of the OOBE.

Redpill
A tool named Redlock can be used to unlock all of the Redpill levels on this build, including the Start screen.

The Metro in this build is identical to its alternate compiles. However, MS Help has been removed.

Aero
This build appears to have a slightly broken Windows Aero theme, with only the top portion of the window frame using the blur effect, leaving the side borders transparent.

Advanced Vector Extensions CPU bug
This build's x86 compile will not boot on some CPUs with the Advanced Vector Extensions (AVX) instruction set due to a bug where a CPU triple fault occurs immediately after the boot screen is first displayed. A workaround is discussed later in the article.

Aero Glass in Home Basic
This build automatically enables Aero Glass transparency even when installing the Home Basic SKUs, which is not supported by default. However, changing the color scheme (visual style) to another one and then back to the default one will disable Aero Glass.

Compiler
This is one of the first builds to be compiled using a new compiler. However, the problems surrounding it at that time resulted in the build becoming unbootable on certain hardware, as the boot loader does not properly function on modern x86 CPUs, namely Intel processors with the AVX instruction set and a select number of AMD CPUs. As a result, a CPU triple fault occurs resulting in either a crash on a hypervisor or a reboot on real hardware.

Patching winload.exe to run on Intel processors with AVX
In order to properly enable SSE instructions for machines using Intel processor with AVX, the 9th bit in Control Register 4 (CR4) must be turned on. The following code is executed and is located in winload.exe at offset A552: By default the following bits are set in CR0: Protected Mode (PE) (0x00000001), Monitor co-processor (MP) (0x00000002) and Extension type (ET) (0x00000010), with no bits in CR4 set initially, so the need to turn on the 9th SSE bit (i.e. OR with 0x600) should be done, but due to limitation in this piece of code, a rewriting needs to be done and the following approach may be used instead: As a disclaimer, patching winload.exe with these changes will invalidate signatures and thus requires  to be enabled in the BCD in order to boot with the patched winload.exe, as well as ownership of the file in both   and   need to be altered in case file replacement was not possible.

VMware Workstation
For another workaround on the Intel SSE bug that does not involve patching and disabling security checks, the compatibility level must be set to version 7.x or lower in order to boot this build. In addition, the following block of code must be added to the VMX (virtual machine configuration) file in order to allow this build to boot on modern Intel CPUs:

The above configuration is mostly not required if the host machine has an AMD processor, and as such only requires the compatibility version to be changed.