ECS P6BAP-A+ is a weird motherboard because was released in 2000, when AGP 2.0 (AGP 4X) cards were available, but it has an AGP 1.0 (AGP 2x) slot. This slot has keying to prevent insertion of a card that doesn't support AGP 1.0's 3.3V signaling voltage. Most AGP 2.0 GPUs are backwards compatible with AGP 1.0. That's why most AGP 2.0 cards' connectors have two notches; the notch on the left allows insertion into slots that are only compatible with AGP 1.0, and the notch on the right allows insertion into slots that are only compatible with AGP 2.0. Cards and motherboards that are compatible with both AGP 1.0 and AGP 2.0 are called AGP Universal.
I have a GeForce 2 (AGP 2.0) card and a 440BX (AGP 1.0) motherboard; I have experienced zero compatibility problems when I use them together because the GeForce 2 is AGP Universal.
However, compatibility between a card and a motherboard is never 100% guaranteed, even when their specs indicate that they should work together. Back in 2000, a friend of mine bought a GeForce 2 card and a Socket 370 AGP motherboard (I can't remember which motherboard), and the card and the motherboard were incompatible with each other. He couldn't determine why. Next, he bought a Rage Fury MAXX (AGP 1.0) card to replace the GeForce 2, and the Rage Fury MAXX worked fantastically with his motherboard! So even AGP Universal cards might be incompatible with a quirky motherboard in rare instances; you just have to experiment.