Mini6410 nand/sd boot switch

Can you plz describe how this switch works?
As i see in table 3-1 in s3c6410 user manual if OM[4:0] = 1111x, IROM boot
is selected. If GPN[15:13] = 000, IROM boots from SD/MMC ch 0. As i see in
schematic this is one position of S2 switch. In another position of S2 it
pulls OM3 & OM4 to gnd. So OM[4:0] = 00110. As i see in User Manual this is
reserved combination. So i wonder how it is booted from nand? And how it
boots from SD?
I get it work booting from NAND with last git version of u-boot. Now i try
to create small (<8K) bootloader to start u-boot from SD, but SD-Flasher
won't flash my bootloader, becouse image is to small. I also try
uboot_writer (with i was using wirh s3c2416), but SD card won't boot.

I found this page. It described what you want to known.
http://blog.csdn.net/nanjianhui/article/details/4230565

The first picture is for s3c6410, the second picture is for s3c6400.

I am studying mini6410 board and 

Mini6410 schematics and s3c6410 data sheets seems to be bit confusing.

Mini6410  SC36410    S1_ON  S1_OFF

SELNAND    XSELNAND  1  1
OM4    XOM4    0  1
OM3    XOM3    0  1
OM2    XOM2    1  1
OM1    XOM1    1  1
OM0    XOM0    0  0
BOOT_EINT15  XEINT15/GPN15  0  0
BOOT_EINT14  XEINT14/GPN14  0  0
BOOT_EINT13  XEINT13/GPN13  0  0
DBGSEL    XDBGSEL    1  1

From s3c6410 datasheet

         OM[4:0]
S1_ON  = 0011     RESERVED
S1_OFF = 1111     SD/MMC

Why S1_ON setting seem to be reserved, as it should configure NAND? Is
there a problem with schematics?

I found also this: http://www.friendlyarm.net/forum/topic/2802

Hi,

Somebody thinks certain configurations are "reserved" because
Samsung wants to hide something, maybe better description of
boot settings can be found from s3c6400 data sheet?

Google translated article about booting s4c6410:

http://translate.googleusercontent.com/translate_c?hl=en&rurl=transl...