 As all sun4c machines are now older than the battery life of this chip, a substantial number of these systems now refuse to boot.Additionally, the sun4c design used the reserved bits in the M48T02's NVRAM in a non-standard way; since later revisions of the M48T02 chip exert stricter control over these bits, a current M48T02 will store the NVRAM data, but the RTC will not function correctly and the system may fail to auto-boot.Due to incompatibilities with modern M48T02s, it is common to modify failed NVRAMs by cutting into the encapsulation and patching in a new battery.