What is a “Low Difficulty Share” error?

Question

I am trying to mine on an old AMD Radeon HD 57xx GPU with Catalyst version 15.7.1 on a Windows10 x64 machine.
Claymore's CryptoNote GPU Miner v9.4 receives the following error from the pool

{"id":1,"jsonrpc":2.0","error":{"code":-1,"message":"Lowdifficultyshare"}}

This topic on bitcointalk suggests to use a particular algorithm for such card (-a 3 switch).

What does "Low Difficulty Share" error mean in this context?

Answer 1

Usually that error means the share your miner submitted was garbage, and didn't actually verify on the pool. Sometimes it means the share was submitted too late, and the pool has already moved on to the next block. But if you keep getting it over and over, then your miner code is broken (or you're using the wrong algorithm).