PS/2 Model 30 286 and the DS1287

I recently acquired an IBM PS/2 Model 30 286, type 8530. Upon powering up, after it completed the memory count/test, it stopped with error 161 and 163. 161 means system options not set/dead battery, 163 indicates time & date not set. This means that the CMOS battery is dead. It must be replaced and it’s memory initialized.

To re-initialize the chip’s memory with the correct settings for the computer, IBM provides a “Starter Disk” to set the system configuration and configure other settings. On older systems, these settings would be done via switches and jumpers. A disk is used as a cost saving measure, the setup program should in theory be needed infrequently and putting it on a floppy saves EPROM space.

When booting from the Starter Disk the setup program runs automatically and detects a problem with the nonvolatile memory and proceeds with automatic confirmation then restarts. Upon restart, the same 161 and 163 errors appear. I was hoping that while powered on it would retain the settings, but with a dead battery, it will refuse to start.

In this computer, the real time clock (RTC) and battery backed memory, which stores the system configuration, is provided by a Dallas Semiconductor DS1287 module. The DS1287 is a DS1285 RTC IC with the needed crystal and battery permanently attached in a potted package. This is presumably done to save board space. When it’s battery is dead, the whole module must be replaced. New DS1287s are not longer available.

Fortunately, there are some options. The DS1287 can be cut open to reveal it’s battery connection and a new battery connected externally. Info on how to do that and where to cut can be found here. Another option is the DS12887, these have the same pin-out, same I/O interface, clock registers in the same locations and NV memory (though it has more, witch the compute will simply ignore). These are still available at Digikey. I chose an option somewhere between these two. The DS12887, is a DS12885 with battery and crystal permantly attached in a potted module, just like the DS1285/DS1287. I had an extra DS12885 and battery holder left over from RTC for the IBM XT project I’m working on.

Below is the result of connecting the battery holder and crystal to the DS12885. The crystal was salvaged something else. The battery holder and crystal are held in place with epoxy and some 30AWG wire to connect the batter holder. Several pins on the DS1287 are missing, those were also removed to avoid any potential problems.

With the new RTC module in place, the system was powered up and again showed error 161 VERIFY and 163, however, this is expected since the memory and clock will be invalid. Running the Starter Disk again performed automatic configuration. Upon reboot, it displayed error 163, indicating that the date and time were not set. It still did not boot and wanted the Starter Disk inserted. This time the program ran and gave options to change various settings, including the date and time. With the date and time set, it now booted. So it seems, this computer requires a valid time to boot, it doesn’t revert back to some default date/time if it’s not been initialized.

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