Part of the SPARCstation line of workstations from Sun Microsystems.
The SPARCstation 2 uses an M48T02 battery-backed real-time clock with RAM chip which handles the real time clock and boot parameter storage. The only problem with this chip is that the battery is internal, which means the entire chip must be replaced when its battery runs out. 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. It is also possible to replace the entire encapsulation, which also contains a 32.768 KHz clock crystal. Repair modules such as the open source Glitch Works GW-48T02-1 exist to make repairs neater and maintainable over time, avoiding the need to repeatedly modify old NVRAM modules.
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