Windows – Why does Windows still have the BSOD on Ctrl+Scroll+Scroll “feature”

bsodcrashfreezewindowswindows-registry

Background information

While Windows XP came out I heard about a testing feature that existed to manually cause a BSOD (Blue Screen Of Death). I also heard this was supposed to be removed in XP Service Pack 2. It didn't get removed. It's also in Vista, Windows 7, and all later Windows versions. To enable the feature, navigate to this Registry location:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\i8042prt\Parameters

Add CrashOnCtrlScroll as a REG_DWORD with the value of 1.

Next, reboot. Finally, press Right Ctrl+Scroll Lock+Scroll Lock on any PS/2-compatible keyboard. You'll get a BSOD.

My question

Why is this feature still here?

Best Answer

It's there to allow a break into the Kernel Debugger or generate a kernel-mode dump file. Typically an expert would want to do this when the OS looks locked up and won't even respond to CTRL+ALT+DELETE in order to get the dump file and investigate it for which driver is having trouble.

It's logically equivelent to calling the kernel API KeBugCheck with bugcheck 0xE2 (MANUALLY_INITIATED_CRASH). Also note that the reg values can be set in different reg keys for the USB (kbdhid) keyboard driver versus the ps2 (i8042prt) driver. There is more information on that and customizing which keystoke is used in KB Article 244139.

Since this is implemented in the actual keyboard drivers, I don't expect this would work from and RDP session even if it was enabled.