README.md

Disable BD PROCHOT on MBR bootstrap code

What is this?

This is the MBR version of the Disable BD PROCHOT UEFI extension

It is made by modifying Windows's MBR bootstrap code, which is used in Windows 7, 8/8.1 and 10 (therefore, it is compatible with all these versions of Windows).

This mod uses bootstrap code from here

Why?

ThrottleStop is loaded after the OS has finished booting, which means your entire OS loading is still done extremely slowly.

This doesn't mean ThrottleStop is no longer needed.

Entering ACPI S3 state(suspend) causes the BD PROCHOT MSR bit getting re-enabled. You need to use some userspace tool for disabling BD PROCHOT for such cases.

In case of Windows, use ThrottleStop.
In case of macOS, try SimpleMSR

How to install

Compatibility: Windows 7 / 8 / 8.1 / 10

1. Make sure you are using MBR boot mode (or "Legacy" boot mode on modern mainboard BIOS)
2. Download BOOTICE and run as Administrator.
3. Select the disk, then Process MBR -> Restore MBR
4. Choose boot-windows.bin as restore file
5. Make sure that "Keep signature and partition table untouched" is selected
6. Choose "Restore" and reboot your computer

How does it work?

The following code is added into windows.asm

MOV ECX, 0x1FC
MOV EAX, 0x4005E
XOR EDX, EDX
WRMSR

In order to fit the bootstrap code into 446 bytes, The following messages have been changed:

LOADING_ERROR_OFFSET: EQU ($ - $$) % 0x100
LOADING_ERROR: DB "Error loading OS", 0     => Original: "Error loading operating system"
MISSING_ERROR_OFFSET: EQU ($ - $$) % 0x100
MISSING_ERROR: DB "Missing OS", 0           => Original: "Missing operating system"

Compile the assembly file using nasm.exe -f bin windows.asm -o boot-windows.bin