It’s really not true anymore that PTX is forward compatible. There’s a subset that is but any of the new interesting interfaces that have been added are not for

It’s really not true anymore that PTX is forward compatible. There’s a subset that is but any of the new interesting interfaces that have been added are not forward compatible and change in each microarchitectural revision. Most of the reason you’d drop down to PTX anyway is to use those; otherwise compilers are fairly good these days and it’s rarely the case you’ll see PTX unless you’re profiling.