[Kat Manton]

Part I

Old Suns (and a few other old machines) use a SGS-Thomson (formerly Mostek) 'Timekeeper' integrated SRAM, real-time clock, crystal and battery. (Types include M48T02, M48T08, M48T18; earlier ones were prefixed 'MK'.)

The system's MAC address, host ID and configuration information are stored in this NVRAM; the lithium cell lasts around 10 years and, when it dies, causes all manner of problems including a MAC address of FF:FF:FF:FF:FF:FF and a system which won't boot. It also appears that the design has been changed and some Suns refuse to work with the new ones.

There's more information in the Sun NVRAM/hostid FAQ, including how to reprogram new/repaired ones on several machines.

Google brings up a few pages detailing repair of the things but some attempts look a little crude and at least one appears to discard the crystal, leaving the clock inoperative.

So I thought I'd detail one of my recent attempts. I've done several over the last decade and have refined my methods.

Here's the offending article; this is one of the two from my SPARCserver 1000E.



According to ST Quality Note QNSR9701, the Date Code H994K9440 and Encapsulation Code HT3034A date it to 1994; no wonder it's dead!

For this recipe, one will require:

• Small vice
• Junior hacksaw
• Needle files
• Craft knife (X-Acto etc.)
• Self-adhesive copper foil tape
• Surface-mount CR1632 coin-cell holder (Renata SMTU-1632-1)
• Lithium coin cell CR1632
• 32.768 kHz watch crystal
• Solder, soldering iron, patience, coffee, etc.

Buried in ST Application Note AN934 TIMEKEEPER calibration I found:

At STMicroelectronics, the real-time clock has an internal capacitance of 12.5pF (except for the M41T6x device, which has an internal capacitance of 6pF) across the crystal input pins.

So I got watch crystals specified for a load capacitance of 12.5 pF. I'm currently reserving judgement on whether or not these are suitable, I'll have to observe how well it keeps time with the power off. It's not really a major issue as, although the system time is set from the real-time clock when the OS boots, correcting it is simply a matter of executing 'ntpdate' during system initialisation with a local or Internet NTP time-server specified.

Now, on with the destruction. The first stage is to remove the potted housing containing the cell and crystal, leaving pins protruding to which the new parts can be attached.

The crystal is located at the end adjacent to pin 1, the lithium cell is at the opposite end.

I started at the cell end; the cell is quite close to the end of the package making this end slightly trickier to separate.

First, I cut in from the end, working carefully until I felt the metal pins. (If it's ancient, failing to keep time and retain configuration information, there's unlikely to be any danger in short-circuiting the cell. If in doubt, cut at an angle so the saw only contacts one pin at a time.)



Now I knew where the pins were, I could cut in from the top until I felt the cell, make two angled cuts, then break off the encapsulation by levering it with a small screwdriver (it's fairly soft but also brittle.)



Next I made an angled cut to separate this end.



Then I turned the device around and repeated the process at the other end.



Continued in Part II...