It's fairly trivial, but still significantly harder than computing a single CRC.

From stackoverflow:

Because a 32-bit CRC yields only 2³² (approx. 4.29 billion) possible outputs, the Birthday Paradox dictates a 50% chance of an accidental collision after processing just ~77,000 unique inputs.

I've done it for shits and giggles and from memory it took my desktop PC maybe 10 minutes to generate a collision.

You're missing the point though.

Noise is not the only thing they should be protecting against.

The point is that AMD is executing code based on checking using an algorithm that has barely any protection from malicious inputs, which is stupid, and not fixing it just compounds that stupidity.

A cryptographic signature protects against both noise and malicious inputs.