[Gta04-owner] Antwort: Re: Amazing adventures with a brandnew GTA04...

Dr. H. Nikolaus Schaller hns at goldelico.com
Thu Feb 9 14:55:47 CET 2012

> I started with a GTA04A4 with empty Flash and a newly bought 16GB SD-Card Class 10. I reformatted the SD-Card manually because I wanted to get practice. So I called "fdisk" and set up 255 "heads", 63 sectors and 1947 "cylinders" (-> Why on earth is this necessary on an SD-Card??).

Some technical background:

The OMAP processor has a Boot-ROM that knows how to find a binary block of data on a specific position of a SD card. I.e. it does not really know about file systems, but about a "raw" access.

To enable us to mount and copy files into a file system, but make it be stored at the specific position on the SD card, needs to format it in a special way and copy the file MLO as the first one.

Dhe Boot-ROM can load it into SRAM (64 kByte on Chip RAM). The MLO code loaded into the SRAM is a stripped down U-Boot. But that U-Boot knows about the FAT file system, and can therefore load u-boot.bin from any location on the SD card (as long as it is in the FAT partition).

By the way this is the reason why the file is called "MLO". It is MMC LOader. (MMC ~ SD). Because it comes through the MMC interface and loads U-Boot from there.
There is also X-Loader which loads U-Boot from NAND flash. And it is intended to be flashed into a specific position in NAND flash so that it can be found by the Boot-ROM as well.


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