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But that doesn't prove he's using a GPU the name would imply he has access to some massive CPU resources. He might be someone at a University or with access to a supercomputer.

Maybe because it's summer there is some downtime on whatever supercomputer they are using.

If this is true, I hope someone releases a public version. Otherwise, a small group of people will have a complete monopoly on mining, which will not be healthy for the steem economy.

It doesn't prove it but it's a plausible theory that someone has figured out how run the steemd program on a GPU and is now running it on a powerful GPU rig. The steemd program is open source on github. Someone with moderate to high c++ programming skills could adapt this code to run on GPU using something like CUDA or OpenCL. This could theoretically yield hash rates 10 fold and on a multi-high-end GPU rig you could have multiple GPU's on one system, yielding 600k-1200k.

You are right but it proves that the 31 sequenced places in the queue are coming from one machine.