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  • Mon 2019.04.15

    Back in the eighties, when we had the luxury of doubling our NOVRAM capacity to a whopping 1024 bytes, we made sure we wrote an entire page to maximize the number of bytes that would get written in one cycle. For a 4 page 512 byte chip, four arrays of 32 bytes each made a page, so we would fill those over time in RAM, then write that page P0. On the second write, we advanced to the next page P1, and the third and fourth the same way P2 & P3. On the fifth page write, we started over, erasing the first page written P0. In this way, we used one cycle per write for a 128 byte page rather than 128 cycles for each of the individual 128 bytes.

    The Manufacturer Guarantee

    The rough rule of thumb was one page write each hour for one year, roughly ten thousand.

    365 days in a year
    24 hours in a day
    8760 hours in a year

    Therefore, for a ten hour work day, a three year life expectancy.

    Moore's law, doubling capacity while halving price every eighteen months, allowed obsolescence to force an upgrade to the hardware, an excuse to then greedily use that extra memory. ;-)


    NVMC — Non-volatile memory controller
    nWRITE,BLOCK Amount of writes allowed in a block between erase

    The 181 value indicates the number of writes before an erase must be performed. One then could write all 256 32 bit words, one by one with an intermediate erase.


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