My HW errors are almost non-existent no matter what freq I pick but all 3 miners appear to max out in the low 440's. I tried 250mhz and it appeared to be running at 470 but then overnight the avg came down to like 450 so I went back to 218. This is with all 4 PCI-E plugged in so maybe firmware update or some more tinkering can push the numbers up a bit