The interrupt latency has been reduced to such an extent as to make it negligible. Many of the resources that are not needed early in the boot sequence are no longer in the ToolBox ROM Image, and more will be removed as schedule permits. The NewWorld Architecture puts the ToolBox ROM Image in RAM, and marks it read-only. Although the image is 4 megabytes in size, not all of those 4 megabytes are in use. The partitioning scheme is part of the CHRP specification.
PRAM refer to offsets with that partition.
See the New Name Registry Functionality section for more details. The USB Manager is in a NewWorld ToolBox ROM Image, along with class drivers for USB hubs, keyboards, and mice. ADB Macintosh computers no longer always include ADB hardware. For compatibility, the ADB Manager still functions, treating USB keyboards as a variant of an ADB keyboard. This added compatibility does not allow all ADB devices to work as if ADB hardware still exists, even if a USB-ADB conversion device is attached to a USB connector.