To check the CPLD version
cat /proc/balloon_board
This should show 0x0a or greater.

Although I can't be certain (since I'm not sure which Bootloader you
were using) the reseting every 500mS or so is likely to be a symptom of
an under performing power supply. Does your PSU have a current limit
setting? If so
you should set it to 500mA to be on the safe side. Alternatively the PSU
may not be good enough to handle the peak currents without voltage dips,
even if it claims a higher continuous rating.

Assuming you have a standard Guralp build, then you have a CF card slot
and a backplane connector. Do you have a card in the CF slot or anything
connected to the backplane? (If you don't have standard Guralp build
then please advise what is fitted, in particular if you have the 3v3
regulator on board i.e. two MAX604's rather than one).

If you have a WLAN card in the CF slot then you will need to have a good
PSU since Tx'ing on most WLAN cards causes 500mA peaks in addition to
the Balloon board consumption, this can often cause the card to fail
with poorer PSU's.

Good Luck

David Bisset
iTechnic Ltd.