Windows doesn’t boot and all you’re seeing is a black screen after turning on the computer with the power button.

If this sounds familiar, read on.

Given this website is dedicated to USB (Universal Serial Bus) technology, here is a USB-related tip that could explain the black screen during boot.

Check your computer to make sure a USB flash drive is not connected at the time of power up. If you have a USB drive connected, disconnect it and try again. If this resolves the issue, then you likely have a bootable USB flash drive and your BIOS is configured to boot from USB. Both of these issues can be corrected.

The simple solution is removing the flash drive. But if you want to fix the problem permanently, there are a few steps you can take.

First, you can remove the boot code from your flash drive. Unfortunately, you cannot do this with a simple format or even a full format. You will need to clean the flash drive using DiskPart. This process wipes the device of boot code so it becomes a standard mass storage device rather than a bootable device.

Do the following (note: this will remove all data because the file allocation table will be erased):

• In the Windows search bar, type cmd
• From the Command Prompt window, type diskpart
• Type list disk
• From the list, identify the USB flash drive and its disk number
• Type select disk X (replace X with the correct disk number)
• With the flash drive selected, type clean

Your flash drive is now clean of boot code. However, the USB device is not yet ready for use. When you clean the flash drive, the file allocation table is removed, so Windows will prompt you to format the drive.

Navigate to your flash drive and attempt to access it. Windows will request to format the drive. Proceed with the format and the USB drive will then be ready for normal use.

The final step, if you want to fully resolve this issue, is to update the BIOS setting so the computer does not attempt to boot from a USB mass storage device by default. This step varies by manufacturer, and you may need to research the correct key to access BIOS during startup.

In this example, the Dell keyboard command to access BIOS is pressing the F12 key as the system powers on. Once inside the BIOS, locate the boot sequence settings and ensure the USB flash drive or mass storage device is not set as the first boot option. The first boot device should be the internal HDD or SSD (C: drive). The image below shows an example.

TLC memory writes slower than MLC memory because it stores three bits of data per cell, rather than the one bit stored by SLC and the two bits stored by MLC. Writing three bits of data to a single cell requires more complex programming than writing one or two bits of data, resulting in slower write speeds and shorter endurance levels. In addition, the number of program and erase cycles that TLC memory can endure is significantly lower than SLC and MLC memory, further reducing overall write performance.

More complex programming is required because each cell can hold three bits of data (with TLC memory). Because of this trait, when new data is added to the cell, the original data must be erased, remembered, and then written back to the same cell, in addition to the new bit of data being added to the three-layer cell. The speed at which a memory block gets erased depends on the type of memory being used. Generally, Single Level Cell (SLC) memory erases the quickest, while Multi Level Cell (MLC) and Triple Level Cell (TLC) memory take longer due to their increased layers. As a side note, the size of the memory block, as well as the type of controller being used, can also affect the speed of erase operations.

The five steps when writing to memory space in TLC memory are as follows:

• Erase – The existing data in the memory cell must be erased before new data can be written.
• Program – The new data is programmed into the memory cell.
• Verify – The new data is verified to ensure it was written correctly.
• Refresh – The memory cell is refreshed to reduce the risk of data corruption due to charge leakage.
• Read – The data is read from the memory cell to confirm it was written correctly.

If additional data is to be written to another bit of the same cell in TLC memory, the existing bits must be erased first and then written back along with the new data. This overhead in processing slows down the overall speed of the device and directly affects performance.

To get a bit more information about SLC memory, please visit our original post on the topic from 2006.