Windows 8 build 7985 (fbl core1 kernel cptx.110419-1745)

Windows 8 build 7985 (fbl_core1_kernel_cptx.110419-1745) is a Milestone 3 build of Windows 8. The x86 installation media for this build was first shared on 28 June 2022, followed by its public debugging symbols the next day.
==Editions and keys==
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 ==
=== User interface ===
==== Redpill-specific changes ====
The main Start screen user interface now includes the "Start header". The Aero theme has also been updated to feature a new design with sharp window corners and flat buttons, making it more resemblant towards the final look of the Windows 8 user interface.
==== Miscellaneous ====
*The boot screen's status message size has been slightly increased.
*All sample content from Windows 7 has been removed.
=== Bugfixes ===
==== Desktop Window Manager ====
The Windows Aero visual style's atlas no longer breaks when attempting to composite blur, and glow effects on caption bar text now renders properly.
== Bugs and quirks ==
=== App tiles ===
Some app names (such as Control Panel, Chess Titans, Defragment and Optimize Drives, etc) may be truncated by normal sized tiles.
=== Networking bug ===
Enabling networking in hypervisors may cause a 0x133 BSOD.
=== Advanced Vector Extensions CPU bug ===
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 is the last build to contain this bug.
This problem can also present itself as three bugchecks occurring one after the other, with different error codes overwriting each other on the screen.
=== Start screen ===
The desktop application tile is treated as if were a native Metro application despite it not being one. As a result, it is possible to "uninstall" the desktop, although nothing will happen if attempted.
=== Windows Setup ===
* This build must be installed on either an IDE or a SATA hard drive as SCSI disk devices will not be detected properly.
* On some machines, this build may take a significant amount of time to boot.
=== Boot manager ===
As the kernel/boot loader does not call any code to clear the video buffer early within the boot process, any graphics that are displayed in the boot screen may overlay themselves on top of the last frame sent by the boot manager. This problem is easily observed when loading into a ramdisk boot image or while loading into setup.
=== Taskbar ===
The Your Look tile has a white trail in the left and white instead of left white up and down.
=== DWM ===
If DWM is restarted when Redpill is enabled, it causes the Start Screen to glitch while dragging/scrolling.
=== General ===
Attempting to restart or shutdown in this build will cause a softlock on VMware Workstation versions 15.x and newer releases. It is generally recommended to force an ACPI shutdown by powering off or resetting the virtual machine from the Power drop-down menu.
=== Logoff error ===
Sometimes, "WinRT UI Window" will prevent the user from logging off.
== Compiler ==
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.
=== 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 A137:
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 ===
==== 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:
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.
== Gallery ==
File:Bug-Windows 8 Build 7997 garbled boot screen.png|Setup boot screen
7985boot.png|Boot screen
Win8 7985 Bitlocker Boot.png|BitLocker password entry
Windows8-6.2.7989-Login.png|Lock screen
File:7985start.png|Start screen
7985charm.png|Charms bar
7985charmsettings.png|Settings charm
7989c2.png|Second accent color
7985share.png|Share error
7985oobe.png|Metro OOBE
Windows8-6.2.7989-BSOD.png|System crash
Category:Windows 8 builds