Windows 8 build 7973 (fbl_core1_kernel_npc)

6.2.7973.0.fbl_core1_kernel_npc.110330-1809
	Build of Windows 8
OS family	Windows NT
Version number	6.2
Build number	7973
Build revision	0
Architecture	x86
Build lab	fbl_core1_kernel_npc
Compiled on	2011-03-30
Expiration date
Timebomb	2011-07-01 (+93 days)
About dialog

Windows 8 build 7973 (fbl_core1_kernel_npc) is a build of Windows 8 that was uploaded to BetaArchive on 19 September 2015^[1] only in the x86 architecture.

Editions and keys[edit | edit source]

Edition / SKU	Key
Starter	7Q28W-FT9PC-CMMYT-WHMY2-89M6G
Home Basic	YGFVB-QTFXQ-3H233-PTWTJ-YRYRV
Home Premium	RHPQ2-RMFJH-74XYM-BH4JX-XM76F
Professional	HYF8J-CVRMY-CM74G-RPHKF-PW487
Ultimate	D4F6K-QK3RD-TMVMJ-BBMRX-3MBMV

Changes[edit | edit source]

Updated the boot screen to include the fish from the wallpaper of Windows 7 builds 6910 to 7231 and a boot spinner, albeit at a slightly larger size compared to later builds.
Changed the startup kernel font from Lucida Console to Segoe Mono Boot.
The system crash screen font has been changed from Segoe UI to Segoe WP.
The boot manager entry is now named "Windows 8" as opposed to "Windows 7".
This is the first build to include the new readable early crash screen saying:

Your computer needs to restart.
Please hold down the power button.
Error Code: 0x0000078
Parameters:
0x80000003
0x812FA944
0x80F748E8
0x80F744B0

Redpill[edit | edit source]

The Redlock tool can be used to unlock all features in this build, including the Start screen.

The Start screen is starting to look vastly different from the previous builds, with the design of the tiles being changed to a look that more closely resembles its final design.
The Immersive Control Panel has been redesigned.
The splash screen for MS Help has been changed to a rather crude one done in Microsoft Paint.
This build features a new File Copy dialog, which has more features than the one in Windows 7, such as the ability to pause the action.
The Metro folder icons and thumbnails seen in build 7963 have been disabled and can no longer be enabled.

Bugs and quirks[edit | edit source]

App tiles[edit | edit source]

Some app names (such as Control Panel, Chess Titans, Defragment and Optimize Drives, etc) may be truncated by normal sized tiles. This bug existed until Windows 8 build 8014.

Advanced Vector Extensions CPU bug[edit | edit source]

Some copies of this build 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.

This problem can also present itself as three bugchecks occurring one after the other, with different error codes overwriting each other on the screen.

Compatibility[edit | edit source]

To install or run this build in VMware Workstation, the hardware compatibility version must be set to versions 8.x or earlier; otherwise, a bugcheck will occur.

Upgrade[edit | edit source]

When upgrading to this build using the new Windows Setup tool, installation might fail. When the Applying computer settings phase starts, a runtime error will occur with C:\$WINDOWS.~BT\Sources\Install.exe, and alt-tabbing after clicking OK will reveal another error saying that Windows could not complete the installation. To install Windows on this computer, restart the installation. In order to upgrade to this build, use the older setup tool located in the sources folder or use Windows Setup files from a different build.

Aero[edit | edit source]

Only the top portion of the window frame is blurred when using the Windows Aero theme, leaving the side borders transparent. This bug persists until the next build.
- This bug affects the Aero Lite theme as well.

Aero Glass in Starter and Home Basic[edit | edit source]

This build automatically enables Aero Glass transparency after installing the Starter and Home Basic SKUs, despite product policies limiting usage of such effects. Changing the current visual style over to a different one (e.g.: Windows Basic) will disable it.

General[edit | edit source]

If using VMware Workstation versions 15.x or above changes in build 7878, attempting to restart or shutdown in this build will cause a softlock. To fix this, use the Power menu from the VM section. This bug persists until build 8008.

Pseudo language pack[edit | edit source]

In this build, the pseudo language pack is present, and it can be installed. This is caused by improper cleanup of the pseudo language pack while staging the build, resulting in leftover files. This persisted up to Windows 8 build 8102 (winmain win8m3 eeap).

DWM[edit | edit source]

After installing the video card driver, Immersive Control Panel will open after using Ctrl+⇧Shift+F9. It will not close unless Ctrl+⇧Shift+F9 is pressed again.

Compiler[edit | edit source]

This is one of the first builds to be produced 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.

Most of the bugs found in this build are a side effect of the new compiler.

Patching winload.exe to run on Intel processors with AVX[edit | edit source]

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 A042:

mov     eax, cr4        ; 0f20e0
or      eax, 20h        ; 83c820        -- Turn on 5th bit, PAE (Physical Address Extension)
mov     cr4, eax        ; 0f22e0        -- Store it in CR4
mov     eax, cr0        ; 0f20c0
or      eax, 80000000h  ; 0d00000080    -- Enable paging
mov     cr0, eax        ; 0f22c0

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:

mov     eax,620h        ; b820060000
mov     cr4,eax         ; 0f22e0
mov     eax,80000013h   ; b813000080
mov     cr0,eax         ; 0f22c0
nop                     ; 90
nop                     ; 90
nop                     ; 90
nop                     ; 90

As a disclaimer, patching winload.exe with these changes will invalidate integrity checks and thus requires Test Mode to be enabled (by setting NoIntegrityChecks in the BCD to on) in order to boot with the patched winload.exe, as well as ownership of the file in both %systemroot%\System32 and %systemroot%\System32\Boot need to be altered in case file replacement was not possible.

Compatibility[edit | edit source]

VMware Workstation[edit | edit source]

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:

cpuid.0.ebx = "0110:1000:0111:0100:0111:0101:0100:0001"
cpuid.0.ecx = "0100:0100:0100:1101:0100:0001:0110:0011"
cpuid.0.edx = "0110:1001:0111:0100:0110:1110:0110:0101"
cpuid.1.eax = "0000:0000:0000:0001:0000:0110:0111:0001"

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.