Specifies the maximum extended upstream transmit power of which this device is capable. A value of zero indicates that the device has no extended upstream power capability. The value specified in this object will be advertised in TLV 5.40 of the CM's modem capability message. This object differs from cmExtendedUsTxPowerCapability from the BRCM-CM-MGMT-MIB in that the value set to this object will be stored in both permanent and dynamic nonvol. The permanent setting will become the new default; if dynamic nonvol is defaulted then it will adopt the value stored in permanent nonvol. Note There will be limitations on performance in extended power mode: 1. The same modulation format must be used for all 4 upstream channels. 2. Distortion will increased. It will comply with DOCSIS requirements, but will no longer comply with the extended Comcast specifications for downstream spurious signals from 54 to 88 MHz. 3. Extended power will be increased for 64-QAM and 16-QAM formats ONLY. 4. Power enhancement will only be achievable on North American low-split systems (42 MHz upper limit).