Promise TX4300 boot problems

[Lawrence Farr]

I've stuck a Promise TX4300 controller in to replace
the marvell onboard SATA that I can't boot off on a
Supermicro server. If I set 2 discs up as Raid 0
or Raid 1 it's fine, But 4 discs as Raid 0+1 is detected, 
installs without any problems, but hangs at the boot 
loader with elf32_loadimage: read failed. I'm guesssing 
the boot loader thinks it's a mirror, not a stripe and
fails to read past the first stripe on the disk?

Anyone come across this or have an idea?