Just wanted to share my testing results from the past two days with my R606 powered by an HP1200. Running on a Raspberry Pi 3B+ over wifi, so it looks like I'm maxxed out on this config as 600MHz is autotuning to 588.
This is damn near a mirror of what I am seeing. My Pi is hardwired just because of proximity.
Good to know that someone is having a similar experience. Time to pull an old desktop out and start fiddling with it.
Thank you for the insight @DieselWeaseI