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Basys 3 abacus demo


Hi guys,


I have been writing PC software for the last 15 years and I now wanted to take a shot at FPGA,

I have bought myself the basys3 board and installed the viva do software,


I followed the instructions for the Digilent abacus demo,

this is a simple binary calculater to show some very basic functions,

I Immediately noticed this takes aboud 15minutes before the program can be transferred to the basys3,

I understand that synthesis takes some time but  15  minutes seems to much for what my patience can handle,

taking into account that the abacus is a simple and uncomplex program, what wil it be with something more complex,


do you guys think this is normal?

the abacus demo can be found here: Download



a bit disappoointed



Edited by Josh
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Sadly, yes it is pretty normal...


Unlike compiling software, generating the configuration files is a lengthy process with lots of hard problems that take time to solve along the way.


The first thing is to building the entire design in memory, and applying optimizations like propagating any constants and identifying and removing redundant logic.


... then decomposing a design into 'the best' set of primitives.


... then reorganising the logic to improve performance by duplicating registers with high performance, or moving registers around in pipelined structures.


...then trying to work out where to place those primitives to give a pretty good chance  that any two that need to be wired together are close together


...then working out how to actually wire them over the limited routing resources, and making sure that none of the connections are too long or take too many hops  (making them too slow).


You can give the tools hints that help speed things up, but the Vivado tools seem to be aimed at improving the performance of implementing large designs by doing a lot of work early on, and this makes small and simple designs take longer to process.


So for quick turnaround, the best bet is to use the simulator - 15 minutes spent writing a reasonable test bench will pay off if you avoid one build cycle.

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