As we predicted some time ago, AMD has finally restored the Asynchronous Compute Queues feature in Catalyst driver for GCN 1.0 GPUs.
Though it did not improve at all the performance in the AMD modified D3D12nBodyGravity sample, looks like last drivers (17.2.1) re-enabled async-compute for GCN1 GPUs. Not sure how much will impact games (Currently my 280 is used as slave gpus for non-game applications), but at least this should cause less problem to developers.
Here's a shot by GPU View, as you can see, the compute queue is back and runs in concurrency with the default queue. Please note that some flip and presentation issues are caused since the GCN1 GPU does not directly output to the monitor (which is controlled by a R9 380X, a GCN3 GPU) and all is handled by WDDM magic.
And here is the log of that small CS test: