Every Sun workstation shipped with OpenBoot PROM firmware that handles hardware initialization, diagnostics, and the boot process. Sun released OBP updates over the life of each product to fix bugs, improve hardware compatibility, and add features. Knowing the last available version for your machine is important because OBP updates often resolved real problems: disk size limitations, SCSI quirks, multiprocessor stability, and Y2K issues among them.
Unfortunately, Sun’s original firmware download site is long gone. OBP update images can occasionally be found in archived collections and through the vintage Sun community, but tracking down the right file for your machine requires knowing what version you need.
Last Available OBP Versions
| Machine | Architecture | Last OBP | Notes |
|---|---|---|---|
| SPARCstation 1 | Sun4c | 2.9 | |
| SPARCstation 1+ | Sun4c | 2.9 | |
| SPARCstation IPC | Sun4c | 1.6 | |
| SPARCstation IPX | Sun4c | 1.6 | |
| SPARCstation 2 | Sun4c | 2.4 | 2.2 is most commonly found; 2.4 adds disk size support |
| SPARCstation 5 | Sun4m | 2.25 | Shared OBP generation with SS10/SS20 |
| SPARCstation 10 | Sun4m | 2.25 | Versions below 2.9 can cause multiprocessor issues |
| SPARCstation 20 | Sun4m | 2.25 | Shared OBP generation with SS5/SS10 |
| SPARCstation Voyager | Sun4m | 2.25 | |
| Ultra 1 | Sun4u | 3.11 | Critical for large disk boot and certain SBus cards |
| Ultra 5 | Sun4u | 3.15 | Fixes IDE disk detection bugs and Y2K handling |
Checking Your Version
You can check the installed OBP version at the
OpenBoot ok prompt:
ok banner
This displays the OBP version, installed memory, host ID, and Ethernet address. If the machine is already booted into SunOS or Solaris, you can get the same information with:
prtconf -V
on Solaris, or by examining the boot messages in
/var/adm/messages on SunOS.
Sun4c Machines (IPC, IPX, SS1, SS2)
The Sun4c architecture was Sun’s first generation of pizza box workstations. OBP updates for these machines addressed SCSI compatibility, memory sizing, and boot device handling.
The SPARCstation 2 is worth special attention. Version 2.2 is the ROM most commonly found in the wild, but 2.4 was the final release and matters for disk size support. If your SS2 has trouble recognizing larger SCSI drives, an OBP update may resolve it.
The IPC and IPX both top out at version 1.6. These are relatively simple ROMs compared to later machines, but the update is still worth having for the improved boot device handling.
Sun4m Machines (SS5, SS10, SS20, Voyager)
The Sun4m generation introduced MBus processor modules and more sophisticated firmware. The SS5, SS10, and SS20 all share the same OBP generation, with 2.25 being the final release. This version added important fixes including better SCSI handling across the board.
The SPARCstation 10 deserves a specific callout. Anything below OBP 2.9 on the SS10 can cause multiprocessor issues when running with dual MBus modules. If you have an SS10 with two processors and are seeing instability, the OBP version should be the first thing you check.
The Voyager shares the same 2.25 final version as its desktop Sun4m siblings despite its unique portable form factor.
Sun4u Machines (Ultra 1, Ultra 5)
The 64-bit UltraSPARC machines used OBP 3.x firmware with significantly more capability than earlier generations.
The Ultra 1’s final OBP 3.11 is critical if you want to boot from large disks or use certain SBus cards properly. Earlier versions may fail to recognize disk geometries or hang during probe on some SBus configurations.
The Ultra 5’s final OBP 3.15 is arguably the most important upgrade in this list. Earlier versions have known bugs with IDE disk detection and Y2K date handling. Given the Ultra 5’s reliance on IDE storage as its primary disk interface, this update directly affects whether the machine can reliably find and boot from its own drives.
Third-Party and Clone Systems
Third-party Sun-compatible systems like the SuperWorkstation SW-40S present a special case. These machines may carry custom or hybrid ROM versions depending on the manufacturer. A clone that reports itself as a SPARCstation 2 (4/75) may not accept a standard Sun OBP update image, or may already have a vendor-specific ROM that differs from any official Sun release. Before attempting a firmware update on a clone, verify the ROM chip type and consult any available documentation from the original manufacturer.