For those who like the details, we've got them here:
Not available to all areas.
Motorola SB4100/SB4200 modems are not compatible with the higher speeds on BigPond Cable Extreme. Customers using these modems will need to purchase a new modem by calling BigPond Activations on 131 282. For new modem pricing click here. For customers using a Wi-Fi modem, the actual download speed will be slower than our top speeds, but customers can still achieve superfast broadband speeds.