> Really? Why the radical departure?
This design was mostly specified by another company who participated
in the engineering costs. In their market, devices are subject to
random security audits of any software on the board. Because of this
requirement, all flash has to be socketed for external verification.
If you look closely, you'll notice even the boot EEPROM is a
socketable DIP for this very reason. Onboard soldered-on flash is out
of the question as it cannot be removed from the device for
verification.
>
> Do you have a special x86 MBR loader for the ARM native boot block
> (plug the card into your windows machine to load up a linux binary
image)?
I'm not sure exactly what you mean. On an x86, the first 512 bytes
contain 446 bytes of arbitrary x86 code followed by a partition
table. On this board, this is exactly the same, except its 446 bytes
of ARM Thumb code. The SD card still has a perfectly valid
DOS/Windows/Linux partition table which is all that really has to be
there to be readable from those OS's. We will probably provide binary
dd images of a bootable SD card for download and also provide a
utility to install just the MBR code on an arbitrary (pre-partitioned)
SD card, but our first priority is getting the company who helped
finance this board design to market.
Currently, we've got 446 bytes that load partition #0 as a kernel
image, partition #1 as an initrd, populates an "ATAG" data structure
Linux strangely demands from its bootloader and then starts the
kernel. Its not nearly as configurable as RedBoot, but RedBoot wasn't
going to work well without onboard NOR or NAND flash for its FIS and
FCONFIG.
Depending on how much time we have before we get our production
boards, we may exchange this 446 byte Linux bootloader with something
else people may be more used to dealing with or more featureful, but
our current creation took relatively little time to create, works well
and is quite quick. In effect we boot straight to Linux from the
BOOTROM-- also, there is no interruption point to change out kernel
parameters to e.g. include "init=/bin/sh" as a boot parameter to
bypass security which fits well with the "high security" marketing
motif of the board.
//Jesse Off
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