Change tiny85 fuses

hi, how do I change the fuses to disable the reset pin?

from the fuse calculator I need to change 0xDF to 0x5F
is there a file I need to edit somewhere to make these changes?
or a sketch I need to upload?

using Mac not windows

boards.txt is the simple answer.
You need a programmer to transfer the values from boards.txt to the ATTiny85. (an Arduino Uno can be configured as such a programmer).
If you get it wrong and need to upload an updated sketch, you need a high voltage programmer to get the reset functionality back. This is more complex.

where can I find “boards.txt” ?

I figured it out

Boards.txt won't get you there, the IDE only sets fuses when doing burn bootloader. But that process also erases the flash.

I was looking into this recently because of pressure from users to add a way to do that to my core, and I came to the conclusion that its not practical to do it through the IDE.

Upload the sketch, then manually call avrdude to set the reset disable fuse.

I used this, GitHub - NiKiZe/AtTiny85HVP: Simple HVP FUSE reset for ATTiny with Pro Micro

I had forgotten this. I did once write a programmer to support a user to go through a complete development cycle on an ATtiny85 where the reset pin was taken over as a GPIO pin. The work flow was rather complex and I came to the conclusion that the ATtiny85 was a very bad platform for developing ATtiny85 applications which needed 6 GPIO pins. I’d also go further and say that dispensing with the reset pin is generally an act of desperation and , unless it is a mass market development, or space is an absolute minimum, simply get a package with more pins.

Agree 1000%
Disabling reset to get anothjer I/O pin is what you do when your back is against the wall - you absoluitely must have one more I/O pin. And you can't go to a part with more pins, because there isn't a higher pincount part with the features you need (imagine if back in the days of the 861 being new and exciting, you needed that 10-bit high speed timer, or you were on an 841 because you needed both 16-bit timers, (the next thing up for that would, I think, have been a 40-pin ATmega). I'm aware of one project doing this (they needed it because the part comes in that itty bitty 3mm package and they were hiding it). Among other things, they discovered that the reset pin when used as I/O is still extremely sensitive to static and electromagnetic noise, and putting a long wire on it caused the whole thing to misbehave depending on ambient electrical noise (as in "use the microwave oven in the same room and it resets").

I always program ATTinys with a TL866 and disable the reset as a matter of course. I don't think there's anything wrong with getting and using a HV programmer if you're going to be doing a lot of ATTiny projects.

I made my own using kicad, sharing for anyone who needs them, they connect to an UNO, a normal programmer and a HV Programmer