[bsder]

Yeah, all. Or so close as to be indistinguishable from all.

If I'm really being pedantic, overflow detection was probably more prevalent than two's complement arithmetic at one point.

Directly from the PDP11 ISA:

BVC/BVS -- branch on overflow set/clear

Y'all need to go refresh your memory/study some history before arguing about this more. :)

[renox]

And you'd better read before replying: I said trap on integer overflow, not branch on integer overflow. The former gives you overflow check 'for free', the latter reduce the code density, which impact the instruction cache, which can reduce the performance. And in the early days, performance was above everything else, CPU being so slow..