Agreed, but this was a working uSD that I ran fdisk on.  It mounted fine on
a linux box but the ROM didn't recognize it.  I can't imagine the ROM code
is doing anything with LSN 0 other than reading the partition table.
Zeroing it and then entering the same numbers with fdisk worked.  I still
find that puzzling.  And a bit scary.

Carl

On Tue, Apr 12, 2016 at 1:16 PM, William Hermans <[email protected]> wrote:

> *Segfault.  What has that got to do with the ROM not recognizing a
>> partition table?*
>>
>
> What Robert said above, but also not necessarily segfault. It's undefined
> behavior, as in no one can say what will happen, until it happens. There
> *is* a very good chance it'll segfault, but there is a chance said code
> could seem to work fine, or even fail silently. I've seen all three cases
> personally.
>
> So we have no idea how the OP's media was cleared, when attempting to put
> the first, and second stage bootloaders on that media. But it seems to be
> clear that the MBR contained trash from a previous partition table. Or
> simply just trash.
>
> On Tue, Apr 12, 2016 at 9:52 AM, Robert Nelson <[email protected]>
> wrote:
>
>>
>>
>> On Tue, Apr 12, 2016 at 11:41 AM, Carl Krieder <[email protected]>
>> wrote:
>>
>>> Segfault.  What has that got to do with the ROM not recognizing a
>>> partition table?
>>>
>>
>> Everything... The boot ROM is pretty basic..if you have noise/etc
>> anywhere where the bootrom expects "something"...  (it's normally looking
>> for a short header)
>>
>> Well, the bootrom can get lost pretty easily..
>>
>> As long as you:
>>
>> 1: /dev/zero the first 1MB of the drive
>> 2: create your partition table ignoring the first 1MB
>> 3: dd the MLO/u-boot.img into the first 1MB
>>
>> You can have pretty much 'any' rootfs format that u-boot supports...
>>
>> Regards,
>>
>> --
>> Robert Nelson
>> https://rcn-ee.com/
>>
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