As you may be aware, Microsoft has released a number of patches for all supported operating systems to protect them from Meltdown and Spectre attacks. These include Windows 7, Windows 8.1 and Windows 10. Unfortunately for AMD CPU users, these patches cause a blue screen of death (BSOD) for those who have an AMD Athlon chip. The OS gives a 0x000000C4 bug check error.
Many users who installed the cumulative update KB4056894 ran into this issue. On computers with AMD Athlon X2 processors the OS starts giving a BSOD.
The only way to repair the OS and get it working again is to uninstall the released patch.
The current situation with KB4056894
Microsoft is aware of this issue. A new knowledge base article, KB4073707, blocks the KB4056894 update installation. Here is a brief description of the update:
Microsoft has reports of customers with some AMD devices getting into an unbootable state after installing recent Windows operating system security updates. After investigating, Microsoft has determined that some AMD chipsets do not conform to the documentation previously provided to Microsoft to develop the Windows operating system mitigations to protect against the chipset vulnerabilities known as Spectre and Meltdown. To prevent AMD customers from getting into an unbootable state, Microsoft will temporarily pause sending the following Windows operating system updates to devices with impacted AMD processors at this time:
January 3, 2018—KB4056897 (Security-only update)
January 9, 2018—KB4056894 (Monthly Rollup)
January 3, 2018—KB4056888 (OS Build 10586.1356)
January 3, 2018—KB4056892 (OS Build 16299.192)
January 3, 2018—KB4056891 (OS Build 15063.850)
January 3, 2018—KB4056890 (OS Build 14393.2007)
January 3, 2018—KB4056898 (Security-only update)
January 3, 2018—KB4056893 (OS Build 10240.17735)
January 9, 2018—KB4056895 (Monthly Rollup)
So, Microsoft is blaming AMD for not following the documentation and for the incorrect chipset implementation. Anyway, the updates are temporarily not available for AMD users.
If you have already installed the KB4056894 update in Windows 7, and the OS doesn't start, you should remove the update, as follows.
Fix Windows 7 BSOD after installing KB4056894
- Before seeing the animated boot logo, repeatedly press the F8 key or Space bar to open the startup settings.
- Select "Repair Your Computer".
- Start the command prompt from the recovery console.
- Type these commands:
dir d: dism /image:d:\ /remove-package /packagename:Package_for_RollupFix~31bf3856ad364e35~amd64~~7601.24002.1.4 /norestart
This will uninstall the update package. The OS should return to a functional state.
Now, check for updates again and hide KB4056894 in Windows Update if you see it again until the issue gets resolved.