Ok, here is the story. It concerns a real DEC XL-266

I played around with the dates under Red Hat 5.1 and after a cold boot I got a NVRAM error, set system time. When entering the menu for the time settings you ended up in a kind of endless loop, saying invalid date/time settings, still no boot.

Replacing the clock chip did not help.

Thus here is what we did after talking to the Dallas support:

The answer from Dallas was the following:

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The DS1225 contains a DS1210 controller:

To erase the contents of the NVRAM module, turn off the power and turn on the freshness seal for the battery to prevent the battery from suppling power to the SRAM. This will wipe out the contents of the SRAM. To turn on freshness seal on the NVRAM controllers, do the following for the different controllers. The customer turning on the Freshness seal is generally not recommended since over-voltage stresses can potentially cause damage to the devices and also once turned on, memory loss will occur with any data stored in the module being lost.

DS1210 - Connect the GND pin to ground and apply -3.5V to the Vcc pin. DS1610 - Connect the GND pin to ground and apply +8V to the Vcc pin. DS1312/14 - Uses a test mode of the chip. From power-up, put 15 pulses (5V for 1312) into the /CEI pin followed by an 8V super pulse, then drop Vcci below Vcctp to turn on the freshness seal. The pulses should be high for 0.8-1.0mS in duration and low for greater than 5nS.

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As we don't have something providing us with 3,5 V we did the following:

We took 3 Mignon Batteries with 1,5 volts an connected them. Plus 1 to Minus 2 Plus 2 to Minus 3 this makes 3,5 V. Don't use Accus, this won't work.

Then we connected Plus to PIN 12 and minus to PIN 24.

Hold this for 5 seconds and the NVRAM is empty.

To figure out the Pin, you look on the chip, there is a white or black little circle on it this is Pin 1.