Dallas chip is not ROM, it's RAM with battery, maybe also RTC.
It's completely internal when Vcc goes down, so you can't test its internal battery without opening its case.
If settings are not permanent you can guess that battery is empty.
If the chip includes an RTC and has low battery the time was usually first to stop functioning.
Normally PC has a setup where default values can be selected by a single button.
Old PCs had it differently and very old PCs had old style HD settings.
Back in the day empty batteries was a regular thing, so how to boot was also noted somewhere.
I had a habit to ink HD number on the back of the case.
If current time and power off was needed inputting time after every power on was irritating very fast.
Some PCs had also an external battery connector.
I remember that it was regularly changed to in use, but can't remember what the actual chip was.
Would like to strip these boards, but it just takes to long
Unbent legs and you have a change.
I tried unregulated hot air fun, it wasn't very nice.
Chips didn't fall out, I had to knock the board.
Finally many were off, but many were also lumped together.
Pros had a small wave pot.
There you had rollers inside a tin and moveable walls.
Rollers were pushing the wave up and over the walls.
Height is critical, so some sort of a jig is also needed.
Don't know how regular hot air thing works.
The body has quite a bit of mass.