Forum Discussion

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

Speed grade and Timequest

Greetings,

I have a design that uses a Cyclone III EP3C25F324C6. I created a new revision of the Quartus project and changed the device to a different speed grade: EP3C25F324C8. However, the Timequest results are all the same. Any ideas what I am doing wrong? Thanks!

4 Replies

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

    hmm, you should not need to make a new project. changing the device settings and recompiling the design should be all that is necessary. i know that when I change from spd grade 8 to spd grade 7 I get more slack in time quest.

    I'd say double and triple check it. Is the failing nodes for the alt tck clk or something like that? Or are you failing timing for part of your own logic? keep in mind if you are passing timing, that quartus is probably not trying to optimize your design further than meeting all of your timing constraints. Meaning it will only do what is good enough to meeting timing for your design for the chosen device and speed grade.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    15 years ago

    The design is not failing timing with the faster speed grade. The problem is that when I switch to a slower device all of the timing results are exactly the same, as if the timing model has not changed. This can't be right so I must be doing something wrong.

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

    --- Quote Start ---

    The design is not failing timing with the faster speed grade. The problem is that when I switch to a slower device all of the timing results are exactly the same, as if the timing model has not changed. This can't be right so I must be doing something wrong.

    --- Quote End ---

    Hi,

    sounds very strange ....

    I would cross-check in the compile summary whether the device is really changed.

    Kind regards

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

    Resurrecting this thread.

    I'm having the exact same problem with MAX II designs. I have verified in the fit report that the device has correctly changed to the proper C, I, or A suffix, and also that the proper temperature range has been selected. I can run any of the three speed grades and always get identical slack reports. Could this be a library issue?

    Thanks,

    Darrell