Thank you kindly Ash and Tyler for your input. Before diving in does anyone want to hazard a guess on how much work will be required to get the MLO on NAND to launch U-Boot and then the Kernel from MMC3?

I'll report back if I'm successful or stuck ;-)

-JR

On Sat, Jul 7, 2012 at 2:44 PM, Ash Charles <ashcharles@gmail.com> wrote:
MMC3 is not, strictly speaking, a 'bootable' interface.  This ends up
meaning that the processor can't boot from an MLO file on this
interface.  With some work, I suspect an MLO on NAND or another
bootable interface could be taught to find code on MMC3 at which point
Tyler's instructions look good.

-Ash

On Sat, Jul 7, 2012 at 9:57 AM, Tyler Jones <tylerjones64@gmail.com> wrote:
> I believe this is possible but have never tried it.
>
> 1. Create a bootable sd card
>
> 2. You need to make a u-boot script
>
> 3. Create a file called bootcmd, and place U-Boot commands in there like a
> script file. For example:
>
> setenv bootargs 'console=ttyO2,115200n8 root=/dev/mmcblk0p2 rw
> rootfstype=ext3 rootwait'
> mmc init
> fatload mmc 0:1 0x80300000 uImage
> bootm 0x80300000
> boot
>
>
> I have Highlighted the parts I think you will need to change, in case the
> archive doesn't like the formatting they are:
>
> 'mmcblk0p2' in setenv bootargs line (most likely the 0)
> '0:1' in fatload line (most likely the 0)
>
>
> 4. Use mkimage to create the boot.scr file. For example:
>
> mkimage -A arm -O linux -T script -C none -a 0 -e 0 -n "Overo boot script"
> -d bootcmd boot.scr
>
>
> 5. Copy the resulting boot.scr to the fat16 partition on the SD card.
>
> I have not tried this but I hope it gets you on the right track.
>
> Please send an update on how this goes,
> -Tyler Jones
>
>
> On 7 July 2012 09:28, John Romeo <bluesmoke73@gmail.com> wrote:
>>
>> I have an expansion card that among other things connects a microSD slot
>> to MMC3 on the J4 Gumstix header. Does anyone have an idea of how I could
>> boot from a filesystem on a card in that slot?
>>
>