thanks!
idk how i missed that
anyway
"cat picore.gz nodejs.gz > catpicore.gz" works
after loading coreutils im using
printf '0x%x\n' $(stat -c%s catpicore.gz )
to get the hexsize from the initrd file
change
cmdline.txt
initrd=0xa00000,$hexsize
and
config.txt
ramfsfile=catpicore.gz
it boots! and node can be started from terminal .