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Altera_Forum's avatar
Altera_Forum
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16 years ago

Use of Resources

In the compilation report where it says logic utilization I am confused.

Is the amount of logic elements used the combinational ALUTs +dedicated logic registers?

As the logic utilization would suggest this is the case.

Or are the logic registers just part of the combinational ALUTs and this is some efficiency thing.

Basically I trying to make an estimate of what my card is capable of. Also in quartus they only talk about the amount of combinational ALUTs.

Thank you in advance.

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

    In the compilation report go to Fitter -> Resource Section-> Resource Usage Summary. There's a lot of good info here.

    The Adaptive Logic Module is great because it's adaptive, but it means there is no longer a black-and-white issue, like the old days of counting 4-input LUTs and registers. For the most part though, you'll have one thing dominating, either Combinatorial LUTs or Registers. The combinatorial LUTs are best to think of as half of the logic in an ALM. So if you have two logic functions, it counts as two. If you have a 7-input function it counts as 2. If you have a 5-input, 4-input, 3-input or 2-input function, it counts as 1. (The 6-inputs have a percentage counted as 2 and a percentage counted as 1, based on other designs, because it assumes logic can be packed with some of them into a single ALM).

    Most designs are dominated by logic, and the registers pack nicely with the combinatorial nodes. Some designs(especially DSP), are register intensive and might have a lot of register only ALUTs. (The ALUT is the combinatorial LUT and the register in half the ALM, whereby if either is used, the ALUT is used). If registers dominate your design, then as you add more logic the fitter can begin to pack them with unrelated combinatorial logic. In Q9.0 there is a section of estimated registers that could be packed with logic(or something like that). Feel free to post that part of your report and ask some questions.