Comment 3 for bug 928580

So this happens because u-boot's code to identify what RAM timings to use doesn't cover the case we report:

http://git.linaro.org/gitweb?p=boot/u-boot-linaro-stable.git;a=blob;f=board/ti/beagle/beagle.c;h=2dd863b4171211c014816a6b858aef9edad59835;hb=HEAD#l179

QEMU reports as a C4 via the GPIO lines, and a NAND manufacturer of Micron with a part ID 0xba. U-Boot's code for the C4 only handles (STMicro, 0xba) and (Micron, 0xbc). Anything else falls through (intentionally or accidentally?) to the XM cases and we end up with the settings for the 512MB Numonyx.

This is a legitimate config found on real hardware: here for example is a boot log I found via google which clearly shows a C4 with an (0x2c, 0xba) NAND chip and 256MB of RAM.
http://lists.linuxtogo.org/pipermail/angstrom-distro-devel/2011-May/004610.html

So it's a U-Boot bug.