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DC_Upd flashes OZ banks in slot 1 in upper half of 512K of the chip; this is the standard - OZ is always located at the top (like in application cards) in slot 1. , hence Rakewell hybrid cards is also supported.
There's no fall-back if a partial update fails; the end-user must recover OZ manually using tools such as RomUpdate. Failures might be due to slot connector problems or simply that the chips shows signs of age.