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1. Introduction

1.1 What the firmware does

The NetWinder contains a 1 MB flash memory chip which holds the program code for initializing the system when first powered on. This `firmware' is responsible for such activities as turning on the video display and loading the core parts of the operating system from disk into memory. It is roughly equivalent to the BIOS on ordinary PC's.

The firmware on the NetWinder is actually a small Linux kernel, with support for hard disk and network access. The main purpose of this `minikernel' is to fetch the main kernel and to set up the root filesystem. The minikernel can load these resources from either the hard disk or from the network.

The minikernel also supports some advanced booting options: a small root filesystem can be stored in the unused portion of the flash memory, or it can be fetched from the network and stored into RAM. Seasoned Linux users will recognize this as a slight variation on the standard initrd facility.

1.2 Terminology

The terms `firmware', `nettrom', and `flash memory' are used throughout the document and generally refer to the same thing, namely the contents of the flash memory chip. San Mehat wrote the firmware and called it `NeTTrom' which is where the name originated.

The firmware has a number of user-configurable parameters. These parameters are sometimes called the `firmware settings' or `nettrom settings'. Perhaps the notation should be standardized, but the wrong word slips out far too often, so you might as well accept both names.

The terms `flashing' or `burning' are used to refer to the process of reprogramming the contents of the flash memory chip. Sometimes it's called `popping' as well, though I will try to avoid that term.

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