SUN Oracle Sparc T4-1 installation problems

Hi,

I'm trying to install OpenBSD 7.5 on SUN Oracle Sparc T4-1 that is known 
or expected to work.

I ask OpenBoot to boot from a CD:

ok boot cdrom

OpenBoot tells me:

The file just loaded does not appear to be executable.

Then asked to net boot with DHCP:

ok boot net:dhcp bsd.rd

My tftpd serves bsd.rd, and then OpenBoot tells me:

ERROR: Last Trap: Fast Data Access MMU Miss

I would appreciate it if someone could help me out.


Thanks & best,
Irek