Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
14 years ago

Config compression makes no difference

I ran my Cyclone 3 design with and without compressed config file

generation & in both cases the .sof file came out to be 350KB. No

change with compression.

Did I miss some Quartus setting or do I just have an uncompressible

design ? How much compression are people seeing ?

22 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor

    Hello, FvM!

    Recently I asked:

    --- Quote Start ---

    How much time will it take to load the content of EPCS4 into FPGA if payload is only ~2Mbit and the rest is filled up with 0xff ?

    The case is that EP4CGX22 is in "40 Mhz internal oscillator mode".

    There are to possible versions:

    1). 4,000,000 bits x 25 ns / 1 bit = 100 ms

    2). ~2,000,000 bits x 25 ns / 1 bit = ~50 ms

    25 ns = 1/40MHz.

    Which one is correct?

    P.S. How to calculate decompression time by EP4CGX22?

    --- Quote End ---

    And You answered:

    --- Quote Start ---

    The latter is right, configuration bitstream load stops after the real data and a few terminating '1' s.

    --- Quote End ---

    Can You please give me any reference to Altera documents where I can find a straight-forward statement, that "configuration bitstream load stops after the real data" and the configuration time is calculated by taking into account only the "real data" ( or payload ) size of .jic file ( which can be seen in the corresponding .map file as END ADDRESS )?
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor

    I'm not aware of a respective statement, it's my observation, which as I assume applies to all Altera FPGA families.

    If you're not sure about, you should hook up an oscilloscope or logic analyser to your development board.