After several years of gathering dust in the cellar, I’ve finally dug out my Ultra SPARC again. Unfortunately, though, it wouldn’t boot straight away. The cause was (or still is) a flat buffer battery in the NVRAM U13. The fault was originally described in the Sun NVRAM FAQ. Just like the Sparc, the page is no longer available online, but can still be accessed via the Wayback Machine.
I haven’t yet managed to track down a new chip to replace it. It’s likely that this won’t be possible any longer. The chips are no longer in production, and even if there are any remaining stocks anywhere in the world, it’s safe to assume that the backup batteries in those have also already exceeded their lifespan. In the meantime, therefore, the information in the NVRAM must be corrected at every boot.
The NVRAM FAQ, in the section General sun4c, sun4m, sun4d, sun4u IDPROM Programming, describes how to programme the chip.
As the OpenBoot environment is unlikely to be familiar to very many people, link provides an overview of the OpenBoot environment’s commands and serves as a valuable reference.