Are you a Sun owner familiar with the message "The IDPROM contents are invalid"? This error points to the RTC (Real-Time Clock) chip that Sun incorporated, which includes an internal buffer battery that often dies after 30 years. "Internal" is a bit misleading here, as the battery is essentially mounted on top, much like a quartz crystal on the other side.
The chip in question, often found defective in systems like the Sun Ultra 10, is the ST M48T59Y-70PC1.
One way to address this is by carefully opening the chip on the correct side, tapping into the conductors, and then mounting a coin cell battery.
However, there are other methods! In this article, we'll explore the RTC chips used in various Sun systems and identify currently available chips that can serve as replacements. This information is a combination of online research and my own findings.
| Architecture | Models | Notes |
| Sun4c | SS1, SS2, etc. | Use an M48T02. This chip is still available, though some OBP (OpenBoot PROM) versions (e.g., IPX or SS2 with later OBP versions) forget the date upon reboot. (Distrelec: 173-52-170 - as of May 23rd, delivery time: 32 days) |
| Sun4m | SS5, SS20, etc. | Use an M48T08 or M48T18. The M48T08 is still available new. (Distrelec: 173-71-214 - as of May 23rd, delivery time: 370 days) |
| Sun4u / OBP 3.x | Ultra 1, 2, 5, 10, E450, etc. | Use an M48T59, which is still available, as is the M48T58, which is a compatible replacement. (Distrelec (T58): 173-52-17 - as of May 23rd, delivery time: immediate) |
| Sun4u / OBP 4.x | Blade 100, 150, V120, etc. | Also use an MT48T59, but the MT48T58 doesn't work as a replacement in these systems. Instead, it's possible to use a DS1553, though it's no longer in production. |
Programming New Chips and Sourcing
The new chips need to be programmed with the MAC address and HostID to function correctly. OBP versions 4.x no longer have the necessary mkp and mkpl commands for this. Therefore, replacement chips must first be configured in a 3.x system and then transferred to the newer system. I'll explain how this reprogramming works in the next post.
Later Sun4u machines with OBP 4.x (e.g., Blade 1000) use an EEPROM.
Given the long delivery times from distributors, it's worth checking other sources, such as eBay. Often, these chips come directly from China. While some fellow enthusiasts advise against buying there (due to the risk of fakes), I've had positive experiences so far. (And I somehow suspect that the few EU sellers on eBay are simply reselling Chinese goods at three to four times the price...).