Odds probably the RAM was mismatched, and the BIOS did not choose conservative settings. Also could be voltage mismatch, and then your low voltage modules could fry (unlikely though).
Thanks for the link, indeed it looks quite technical and very complete on the subject. Truth be told I'm far from an expert on power, hence the mistake :-)
Considering the 1 minute interval wouldn't it be better for the battery to use a clock implemented in hardware that boots the chip everytime it's needed?
That is typically what you do, microcontrollers have timers and low-power mode(s) which keep the timers running even though the processor core isn't executing any instructions.
I'm not an expert on power optimization, and I don't know how this is done in micro-controllers. But I would think that the hardware clock would be implemented using integrated analog components (capacitor + resistor circuit) rather than digital logic, to avoid repeatedly switching on and off even just a few transistors.
Apparently external xtal is marginally best (http://www.microchip.com/forums/m341592.aspx); which makes intuitive sense, given that it's exactly the same scenario as a digital watch. 32khz crystal; driver; counter; comparator. Few hundred tiny transistors. Consumption probably less than battery self-discharge.
Odds probably the RAM was mismatched, and the BIOS did not choose conservative settings. Also could be voltage mismatch, and then your low voltage modules could fry (unlikely though).