Magic Rat if you are in Arizona, Cox AZ "upgraded" Preferred and Premier customers to slightly faster speeds, April 21st between 1am-3am, But at the same time reduced and capped Powerboost speeds to approx. 30Mbps. Powerboost now only appears to last for a few seconds and only for the first 3-4MBs.
Before this "upgrade", which changed the config file on the modems. It was possible to achieve up to 100Mbps on a file as large as 50MB using a DOCSIS 3 modem, before Powerboost would kick out. This change is mostly notable with small file burst speedtests and large file graphic intensive webpages.
Sustained downloads though actually should have increased from 12Mbps to 15Mbps for Preferred and 20Mbps to 22Mbps for Premier.
The attached image clearly shows the reduction in Powerboost occurring on the morning of the 21st.
