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Altera_Forum's avatar
Altera_Forum
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17 years ago

Onchip Memory size problem in SOPC Builder

i am using Stratix II GX - EP2SGX90FF1508C3 board.

For a particular application ,built in SOPC Builder i am using three OnChip memories each of 64 KBytes.

now if i make one Onchip memory as 32 KBytes and the other two to 80 Kbytes, i am getting Fitting error in Quartus.

how do we decide the total onchip memory size of the FPGA that can be used.

how should i resolve my issue of using 80 KBytes or more for my application

Thanks

2 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    17 years ago

    Hi,

    this is your error?

    "Error: Cannot place all RAM cells in design"

    Best regards

    Luca
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    17 years ago

    Look at the blocks available in the 90, i.e.:

    4 M-RAMs, 408 M4Ks, and 488 M512s.

    Break your requirements down to depthxwidth and see how they fit. For example, if you'r 32Kbyte is 16kx16, then that would fit into a single M-RAM. If you're 80Kbyte is 40Kx16, that won't fit into a signle M-RAM and would require 2. With two of those blocks, that would push you into 5 M-RAMs and a no-fit. So in that case, you could break your 80KByte into a 32Kx16 that uses one M-RAM, and then build an 8Kx16 out of M4Ks. (The megawiazrd will generally not use different RAM types to build a RAM, i.e. it won't automatically stitch M-RAMs and M4Ks together, which is why you would build it out of two individual RAMs and use the MSB to select which RAM is being read to or written from).

    To put this into an SOPC system, you'll probably have to wrap it in a single file and replace the file that SOPC builder creates. I'm not sure on that one, so maybe someone else has input...