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Well it tells me to look at the docs how to obtain the bootloader and the docs tell me to use mkamsboot.
The manual actually tells you that using mkamsboot is not recommended. But if you insist on doing things the hard way, you will need to either compile your own version from our source code or simply use an older version of the original firmware which the binary you have supports.
Sorry but the utility tells me to look at the pdf and the pdf tells me to use mkamsboot.
Please see http://jcremers.com/rockboxsansamanual.jpg
There are two ways to install Rockbox: automated and manual. The automated way isthe preferred method of installing Rockbox for the majority of people. Rockbox Utilityis a graphical application that does almost everything for you. However, should youencounter a problem, then the manual way is still available to you.
But in that pic i posted it clearly says:
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