[CentOS] CentOS 5.5 Sofware RAID1

I have the CentOS 5.5 install DVD and trying to install with software
RAID1 on two 2TB SATA drives.  The CentOS install only sees one drive.
 This is a Supermicro motherboard with fakeraid turned off in bios.

I tried the trick like so:

dd if=/dev/zero of=/dev/sda bs=512 count=64
dd if=/dev/zero of=/dev/sdb bs=512 count=64

Still no go.  linux rescue console does see both sda and sdb.  Whats going on?