Challenge 5 : calculate total stcell count

 Hi All,


below case will test your practical concepts related to Floorplan.


suppose, there is one design without any macros/IPs with Floorplan Aspect ratio as 1. site row height as 0.169 and site row width is 0.048. in all stdcells, applied keepout : left --> 0.24  ,  right --> 0.24 . left/right side core to die offset as 0.624 and top/bottom core to die offset is 1.014.

for this design placeopt is completed (stdcells are legalized properly).  

After completing placeopt, all Physical/Special cells are removed manually and also stdcell apart from instances with cell reference as INV8 are removed. (i.e. design is having only INV8 ref cells).


stdcell utilization : 0.6 , Total stdcell area : 476.3772 , Total Core area : 793.962

From LEF, area of INV8  : 0.15412800

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What will be Total stdcell count ..?

comment your answer below.

To revise Floorplan concept related to blockages/keepout, Please check below post:

Placement and Routing Blockages: Strategies for Optimal Design Flow






Comments

  1. Shubham GuptaAugust 12, 2025 at 9:30 PM

    The total std cell area = INV8 instance area + other std cells area. Without knowing the detail like how many number of INV8 instances are design, how will we calculate the other std cells count.
    Please let me know if I've understood it wrong.

    ReplyDelete
    Replies
    1. JigneshAugust 12, 2025 at 9:48 PM

      Hi Shubham,

      All are INV8 instances only. Other stdcells are deleted..

      Delete
    2. Shubham GuptaAugust 12, 2025 at 11:33 PM

      Can we assume area of std cell and area of INV8 equal

      Delete
    3. JigneshAugust 13, 2025 at 5:34 AM

      Design is having only 1 stdcell ref, that is INV8 only.
      All instances are of INV8 ref only

      Delete
  2. Aman KumarAugust 13, 2025 at 11:04 AM

    Area of Inv8 cell = LEF Area of INV8 + left keepout margin area + right keepout margin area
    = 0.15412800 + 2 x (0.24*0.169)
    = 0.235248
    Total Std.cell count = Total Std. Cell Area / Area of Inv8 cell (including keepout margin)
    = 476.3772/0.235248
    = 2025

    Let me know if I am right or wrong?

    ReplyDelete
    Replies
    1. JigneshAugust 13, 2025 at 11:42 AM

      Hi Aman,

      As this is 2025 year, 2025 is 💯 correct answer...!!😃
      You are absolutely right 👍 here..
      Main point to understand here is when tool calculates the Utilisation, always keepout values is already considered..

      Delete
    2. Aman KumarAugust 13, 2025 at 4:48 PM

      Thank you Jignesh 😀
      And thank you so much for posting such a great content.

      Delete
    3. AnonymousAugust 22, 2025 at 6:00 PM

      Aman, how did you calculated keepout area ?

      Delete

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