Intel® Quartus® Prime Software
Intel® Quartus® Prime Design Software, Design Entry, Synthesis, Simulation, Verification, Timing Analysis, System Design (Platform Designer, formerly Qsys)
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ModelSim Memory allocation failure




I am trying to generate execution cycle counts for mathematical operations on very large integers using ModelSim. However, beyond a certain input size, I get the following error:

# ** Fatal: (vsim-4) ****** Memory allocation failure. *****
# Attempting to allocate 27986416 bytes
# Please check your system for available memory and swap space.


The largest set of wires I use is about 1.2 million bits. The design involves pipelining multiple channels of 2048-bit numbers for cryptographic applications, so very large bit sizes for wires and regs are unavoidable.

I understand that signals take more memory than variables, so I have tried to use variables in my test bench when possible, but I am not able to use them when connecting modules because they cannot be converted to nets.

I have also tried to simulate my modules with smaller integer sizes and the testbench executes successfully, so I don't believe it's a problem with the code.


I am running ModelSim version 20.1.1 on an Intel Windows 10 machine with 32GB of RAM, but I encounter the same errors using version 18.1.


Is there any way to allocate more memory to ModelSim? I am using the 32-bit version that does not require a license and have read that it is capped at 2GB. Is it possible that the net sizes I have described are using all 2GB? And if so, is there another version of ModelSim (or any other modelling software) that can handle such large simulations? I am a graduate student and may have access to other versions/applications through my institution.


Thank you in advance.


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2 Replies

Hi @sbaj000 ,


1. Have you compiled your design without any error in Quartus?
2. Try using the Modelsim Intel FPGA Edition and check if it works.


The Modelsim starter edition may has limitation as described in the link below.

ModelSim*-Intel® FPGA Edition Software


Best Regards,
Richard Tan

p/s: If any answer from the community or Intel support are helpful, please feel free to give Kudos. 

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I have yet to receive any response from you to the previous question/reply/answer that I have provided.
With that, I will now transition this thread to community support. If you have a new question, feel free to open a new thread to get the support from Intel experts. Otherwise, the community users will continue to help you on this thread. Thank you.

Best Regards,
Richard Tan

p/s: If any answer from the community or Intel support are helpful, please feel free to give Kudos. 

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