What isboot ROM

A Boot ROM or Boot Read-Only Memory is an essential component of a processor chip that contains the first code executed by the processor during a reset or power-up of a device. It is responsible for booting the device and downloading the final customer applications.

What is the function of a Boot ROM?

A Boot ROM is a small part of the masked read-only flash or ROM embedded in the processor that plays a vital role in booting the device and running customer applications. Depending on the configuration of internal fuses or strap pins, the boot ROM may decide from where to load the next piece of code to be executed and how or whether to check it for correctness or validity. It is the first code that is executed after the chip is reset.

How does a Boot ROM work?

The Boot ROM code is permanently hardcoded into the device’s ROM mask during manufacturing. As the device starts, the clock signal and the Vcc power supplies the device, and the processor begins executing instructions from its boot ROM. Typically, the boot ROM initializes the memory and the various peripherals present in the device. Its validation is a critical part of the firmware, ensuring the device runs smoothly and other features work.

How is a Boot ROM verified?

Since the Boot ROM code is a crucial part of the firmware that determines the reliability and stability of a device, its validation is crucial. Validation involves running test patterns through various stages of the boot process to verify the Boot ROM’s correctness and detect any discrepancies. If the Boot ROM fails the validation process, the device will not start, and the firmware will not download the final customer applications.


The Boot ROM is a critical component of a processor chip that is responsible for booting the device and executing customer applications. Its permanent and hardcoded nature in the device’s mask ROM during the manufacturing process ensures that it runs smoothly and reliably. Additionally, its validation is necessary for device reliability and stability.


What is the difference between a Boot ROM and BIOS?

A Boot ROM is hard-wired into the SOC and is executed before any other firmware. On the other hand, the BIOS is a firmware that is stored on an EEPROM, which can be updated at later stages. A Boot ROM is essential for the device’s initialization, while the BIOS manages the computer’s hardware functions.

What happens when the Boot ROM fails?

If the Boot ROM fails, the device will not boot, and the firmware will not download. The device will require repair or replacement of the processor chip, which is a challenging and expensive process.

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