Booting is simply the act of starting up and restarting your computer. During this process, the system undergoes through a series of steps called boot process. It is where its hardware and software ready to go. It loads the OS to the RAM.
Table of Contents
Types of Booting
- Cold Booting: This process occurs when a user turns on the computer from a powered-off state. This is also known as hard booting. A cold boot ensures a fresh start and is often necessary to resolve some certain system issues.
- Warm Booting: It is known as restart or soft reboot. it is the process of restarting a computer while it is already in powered-on state. Warm booting is also commonly used in system updates, troubleshoot and to refresh the system.
When you turn on a computer, it loads the OS to its memory or RAM. First it checks if all parts of the booting process are working correctly, it is called power-on-self-test (POST).
Under POST, the system checks the BIOS chip and complementary metal-oxide-semiconductor (CMOS) RAM. If the POST detects no battery failure, it continues to load other parts of the system by checking the hardware devices and secondary storage devices.
Once it finds the operating system, the BIOS or UEFI hands over to control it, and the operating system begins to load into the memory.
Important system files
Partitions
BIOS (Basic Input/Output System) is stored in your computer’s motherboard. It makes sure everything is order when you turn on the computer.
MBR (Master Boot Record) is a data stored in the first sector of the computer hard drive. It contains information about the disk partitions and also helps to find and load the operating system during the boot process.
GPT (GUID Partition Table) helps to organize the storage of your computer. It is the smarter version of MBR. GPT has bigger sectors for storage and support larger hard drives. Latest version of windows has GPT partition which makes data even safer.
How to Identify Which Partition You Have?
To check, use the following steps:
- Open Start Menu
- Search for Disk Management and Click on it
- Right click on the disk and select the properties option
- Click on Volumes tab
- Check on Partition style, whether it is MBR or GPT
Now you know which partition style the drive uses.
Boot process: BIOS-MBR Method
Windows version like XP, Vista, and Windows 7 used BIOS-MBR method. Newer versions of windows use UEFI-GPT because of the enhanced security and makes data even safer.
The following steps are the working process of system when powered on:
- CPU sends signal, checks BIOS firmware.
- BIOS runs POST to check hardware, loads firmware settings.
- Successful POST, additional adapters integrate.
- Pre-boot completes, detects valid boot disk.
- Firmware scans boot disk, loads MBR, searches for boot info in BCD (Boot Configuration Data).
- MBR triggers Bootmgr.exe, locates and launches Winload.exe.
- Winload.exe loads OS kernel ntoskrnl.exe.
- Kernel loads hall.dll, boot-class device drivers, SYSTEM registry.
- Kernel passes control to Session Manager Process (5MSS.exe), loads other registry hives and drivers.
- Session Manager Process triggers Winlogon.exe for login screen.
- Winlogon.exe initiates Service Control Manager, starts services, drivers, security subsystem, Group Policy scripts.
- Now user gets logged in, Windows creates session.
- Service Control Manager starts Explorer.exe, Desktop Window Manager (DMW) sets up desktop.
Now the desktop is available for the user to explore.
UEFI-GPT
UEFI means (Unified Extensible Firmware Interface).
EFI boot manager starts your computer using UEFI boot process. Boot manager loads drivers and applications including the boot files to start the operating system.
There are Five Phases of booting process
- Security phase - The EFI's Security (SEC) phase manages system reset events and prepares for the pre-EFI initialization (PEI) code.
- Pre-EFI initialization phase - The PEI phase initializes hardware by running PEIMs from the boot firmware volume, creating a Hand-Off Block List (HOBL) with the system resources, and passes it to the next phase, which is DXE phase.
- Driver Execution Environment phase - In DXE phase, most of the initialization occurs. It uses HOBL to initialize system memory and I/O resources. After that, it starts running DXE drivers from the firmware volumes listed in the HOBL. The DXE core provides EFI boot services for loading the executable images and EFI runtime services for managing memory addresses. When completed, it is passed to the next phase.
- Boot Device Selection phase – In this phase, The Boot Device Selection (BDS) checks the boot configuration data. And boot based on the policy. It also works with the DXE to verify device driver signatures. The system loads MBR boot code for legacy BIOS boot or loads the bootloader program from the EFI partition for UEFI boot. Users can also choose the boot device, such as the EFI shell or a UEFI application, from the setup.
- Runtime phase – The system clears UEFI program and transfer to the operating system. During a UEFI BIOS update, the OS uses a small portion of memory to call the runtime service.
How to Convert MBR to GPT?
We can convert our partitions as we needed. When conversion disk should not contain any partition or volumes.
Make sure to back up data on the disk.
Method One – Using Disk Management
- Delete all partitions and Volumes
- Click and hold (or right-click) the MBR disk you want to convert to GPT format, then choose Convert to GPT Disk.
You'll receive a notification once the conversion is finished.
Method Two – Using Command Prompt
- Run Command Prompt as Administrator
- Enter the prompt diskpart
- You will Enter Diskpart, and type list disk
- Select the disk by using the command select disk <disk number>
- Clean the MBR disk by deleting all partitions or volumes using the command clean
- Type convert gpt to convert the MBR disk to GPT format.
You'll receive a message once the conversion is complete.
Conclusion
Understanding windows boot process is essential for troubleshooting and maintaining system performance. Whether it is MBR or GPT, the knowledge of boot process helps to get smooth and optimized performance in your computer.