blueseahaichao

Your concept is wrong, the bootloader is not just for DSP. Here is why:

Most computer systems can only execute code found in the memory (ROM or RAM); modern operating systems are mostly stored on hard disks, LiveCDs and USB flash drives. Just after a computer has been turned on, it doesn't have an operating system in memory. The computer's hardware alone cannot perform complicated actions of the operating system, such as loading a program from disk; so a seemingly irresolvable paradox is created: to load the operating system into memory, one appears to need to have an operating system already installed.

The solution to the paradox involves using a special small program, called a bootstrap loader or boot loader. This program doesn't have the full functionality of an operating system, but is tailor-made to load enough other software for the operating system to start. Often, multiple-stage boot loaders are used, in which several small programs summon each other, until the last of them loads the operating system. The name bootstrap loader comes from the image of one pulling oneself up by one's bootstraps (see bootstrapping).

BlueSeaHaiChao

看来你对BOOTLOADER的作用还不清楚。这里我转摘一段中文论述帮助你理解：

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前阶段做了一次基于ARTMEL at91rm9200引导部分的技术分析，虽主要面向使用at91rm9200板子的的朋友做个简单的推敲，希望起到抛砖引玉的作用。

这里要提及的是at91rm9200内部本身有128k的片内rom,其固化了一个bootloader和uploader, 用来支持程序的下载和引导。BootLoader(引导装载程序)是嵌入式系统软件开发的非常重要的环节，它把操作系统和硬件平台衔接在一起，是跟硬件体系密切相关的。

典型的嵌入式系统软件部分Image memory layout : bootloader , bootloader param, kernel, rootfs

总之, 不同厂商的出的Soc片子在启动方式大都提供片内和片外启动两种方式，一般都是在片内固化一段小程序方便于程序开发而已。