Technical Note No. 98/8 - Memory Management

Technical Note No. 98/8 - Memory Management

The following equations can be used to estimate memory endurance, which is the number of bursts that will fill the data memory. MEM is the memory size, which is roughly 130,000 for DOBIE fitted with 256k RAM (the accurate number is reported as the maximum datafile address at the OPENING SCREEN); 10,000,000 for the 10 Mb flashcard; and 40,000,000 for the 40 Mb flashcard (the accurate number for a flashcard is reported when the card is initialised immediately prior to a logging session).

  • Task 2 (time series): memory endurance depends on number of points per burst, N:

(MEM - 114) / (10 + 2N)

Thus, for N = 1024 for example, the memory will fill after about 60 bursts with 256k RAM; 4,900 bursts with 10Mb flashcard; and 19,500 bursts with 40 Mb flashcard.

  • Task 3 (tide gauge): memory endurance is about 6800 bursts for DOBIE fitted with 256k RAM; 525,000 bursts with 10 Mb flashcard; and 2,100,000 bursts with 40 Mb flashcard. Memory endurance is independent of sampling parameters.
  • Task 4/0 (wave statistics): memory endurance is about 1600 bursts for DOBIE fitted with 256k RAM; 123,000 bursts with 10 Mb flashcard; and 492,000 bursts with 40 Mb flashcard. Memory endurance is independent of sampling parameters.
  • Task 4/1 (spectrum plus statistics): memory endurance depends on number of spectral estimates, NS:

(MEM – 22 – 2NS) / (32 + 2NS)

where NS = N / 2M and M is the merge (see Technical Notes). Thus, for DOBIE fitted with 256k RAM and with NS = 16 for example, the memory will fill after 2030 bursts, and for NS = 128 the endurance is 450 bursts. For NS = 128 and with 10 Mb flashcard the endurance is 34,700 bursts and with 40 Mb flashcard the endurance is 139,000 bursts.

DOBIE computes memory endurance for the current sampling parameter settings using the above equations and reports it during setup. Thus, you can use the above information to plan an experiment, or you can let DOBIE do it for you. When the data memory is full DOBIE will put itself to sleep and the "SLEEP" LED mounted on the endcap will glow red when the magnet is held to the SWITCH, thus alerting the user that the instrument is awaiting data download.

MOG
June, 1998