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AR# 3161

4.2i Foundation Simulator - How much memory does a simulation require?


Keywords: Foundation, functional, timing, simulation, memory, RAM

Urgency: Standard

General Description:
What are the memory requirements of the Foundation Logic Simulator, and what is the maximum time the simulation can be run?


There is no software limit on the maximum time for a simulation, but there is a physical limit in the form of memory. For each signal that is probed/analyzed, any event (a change in value for that signal) will require 16 bytes of memory to store the waveform. This requirement is beyond the memory needed for operation of the Foundation tools. The system requirements specified in our documents are adequate for most simulations; however, if the simulation involves long simulation times and/or a large number of signals to be analyzed, additional memory may be required. (This is the case when an error reports insufficient resources during a simulation.)

For Example:
For a 4 Mhz clock running for 40 ms, approximately 5 Mb of memory is needed just to store the waveforms. If you observe 20 other signals that change at ~2 Mhz, the simulator will require an additional 51 Mb, bringing the needed total to 56 Mb. Alongside the tools and operating system, this can overload the system resources.

Possible solutions:

1. Increase the amount of swap space available to the system. The drawback to this solution is that system performance may be reduced by the increased dependency on the hard drive.

2. Reduce the number of signals analyzed or the length of the simulation.

3. Install more physical RAM.

For more information, please see (Xilinx Answer 12939).
AR# 3161
Date Created 12/05/1997
Last Updated 08/12/2003
Status Archive
Type General Article