LAN works fine, even IPv6.

But both 10.5.1 and 10.5.2 only boot up with cpus=1.

For the 10.5.2 install I realized that something went wrong with EFI.. it didn't get installed at all.
Just saw that EFI wasn't installed at all, and 10.5.2 does not detect the SATA drive, while 10.5.1 does. Maybe you're good with keeping 10.5.1