7501/8501 P5 bit (and DDR)

Hi all,
I am wondering whether or not you can set and read the unused bit P5
on the internal 7501/8501 CPU. I don't have a working CPU to make the
test.
However, I can set and read both the P6 and P7 bits on a 6510 and set
the corresponding DDR bits in the register too. If P6 and P7 DDR is 0
(so, inputs) the port bits read 0, I assume they're pulled down
internally somehow?
Can someone make a similar test on a 7501 please?
Thanks in advance.
Frank IZ8DWF