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When I was using my Win7 desktop and then laptop my performance was very poor. So, I would recommend trying on a PC running Ubuntu 18.04 to verify proper operation. I have no idea what unknown variables MACos brings to the table.
I also have Ubuntu 18.04 on my laptop and they ran perfectly on that OS.
Why is it that T = 550 I can't seem to get it past 550...
On your Pi 4 are you plugging your miner into the USB 3.0 Ports or 2.0 Ports? Are you plugging directly into the Pi 4 or are you using a Hub? Do you have other USB devices plugged in?
I'm plugging my R606's directly into the USB 2.0 Ports. Also my Pi 4 won't boot when the miners are plugged in so I have to boot it then plug in the miners. I don't get a warm fuzzy feeling about that, but I just discovered that behavior.
Edit: I just did a test with the USB 3.0 ports and got about the same performance as the 2.0. The unit that previously tuned to 725Mhz did 718Mzh this time but the one running 750 is still doing 750.