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Observer
Observer
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Registered: ‎02-05-2019

Multiple instances of same VHDL module

Hello,

I am using Vivado 18.3, I have created 4 instances of same VHDL module. 

I have noticed that each instance takes different number of resources, I have checked with optimization off and the results are still same.

 

 

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Teacher
Teacher
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Registered: ‎07-09-2009

So ?

Remember the tools run till they meet your timing constraints,
if one of the blocks has been optimised more than the other, thats expected.

It could also be that there is a problem in how they are connected up, have you simulated ? if the connections are different , then the resources could have been removed / pushed back or even shared.

If you had one that took 2000 luts and the other 4000 luts I might be concerned, your down in such small numbers of LUTS, that I'd not worry,

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Observer
Observer
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Registered: ‎02-05-2019

Thank you for your reply.
Yes I have simulated them and even the functionality of all four instances is fine. They all are working as expected.
I was curious that If the optimization is turned off then why still there is a difference between the resources.
Secondly I can see a trend that on each new instantiation the LUTs are getting lesser, is it due to some resource sharing or what.
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Xilinx Employee
Xilinx Employee
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Registered: ‎05-22-2018

Hi @hamzamuneer ,

I guess you are right it might be because of resource sharing. You can try to disable that in synthesis settings and check the result. Fro more information on resource sharing switch please check page no.12 of below link:

https://www.xilinx.com/support/documentation/sw_manuals/xilinx2019_2/ug901-vivado-synthesis.pdf

Thanks,

Raj

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Observer
Observer
277 Views
Registered: ‎02-05-2019

Hi 

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Teacher
Teacher
252 Views
Registered: ‎07-09-2009

I'm not certain where this is going, at the end of the day the tools are transparent to the user,

As an experiment, why not try making 16 of the objects, that would be interesting to see how the optimisation works,

Would also be interesting to see your code as an attachment,
<== If this was helpful, please feel free to give Kudos, and close if it answers your question ==>