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

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?
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