How to mitigate excessive I/O pins fitter error

Question

I am trying to compile a RISC-V core in Quartus (Pro 19.2), specifically the SweRV EH1 from Western Digital (https://github.com/chipsalliance/Cores-SweRV). I was able to get synthesis to pass with only one extra trick required (https://community.intel.com/t5/Intel-Quartus-Prime-Software/Getting-Synthesis-Error-due-to-undefined-Macros-In-quartus-pro/m-p/661513#M61117 ), but now the fitter is failing due to too many user I/O pins being required. According to the error, the "design requires 1417 user-specified I/O pins" while there are only 624 available on the Arria 10 GT 1150 that I am targeting. This seems to be quite an excessive number of I/O pins required (more than double what is available on a decent sized FPGA), so I am assuming that somewhere in the compilation flow Quartus is finding/creating pins that really shouldn't be I/O, as I can't imagine this design really needs so many pins.

So I guess my questions are, is this a reasonable assumption that Quartus might be to blame for these excessive I/O pins? And if so, how could I go about fixing this, and/or convincing Quartus that there really aren't so many I/O pins required?

Thanks!

amint_intel · Answer

Hello,I don't think it possible to fix this issue with device that you have.  Our FPGA devices have different pins available so I will advice you to check your design so it can fit with your FPGA device. You could also try different FPGA devices to fit with your design.I hope this answer helps. Stay safe!

rlb1116 · Answer

Do any Intel FPGAs support 1400+ user I/O pins? I imagine probably not, seeing as how the Arria 10 1150 (which is not small) has significantly less than that at only 624.

I don't think the problem is that the device has insufficient pins, but rather that a large majority of the 1417 ports "requiring" an I/O pin don't actually need to be seen outside of the FPGA as input or output. A RISC-V core certainly shouldn't need 1400 physical I/O connections.

So my question is more along the lines of, how can I parse the ports identified as I/O down to those which actually need to reach outside of the chip? Assuming I am able to identify these truly necessary I/Os in the design, how do I tell Quartus to ignore the others? Are there any compilation tricks for this or do I need a higher-level wrapper with just the essentials? (The design came with a wrapper as the top-level entity, but this induces the 1400 I/O ports, most of which I believe should not be physical I/Os.)

sstrell · Answer

Look at the top-level HDL code and/or the Pin Planner (Assignments menu) All Pins list to see all the top-level I/O required for the design.  Quartus would not add any additional pins to the design unless you edit the code.

amint_intel · Answer

Hello,

Unfortunately there is no trick to add more pins on Quartus. We have many FPGA lineups that may fit your design.

rlb1116 · Answer

Adding more pins is not at all the route I was aiming for; however, if you would like to point me to an Intel FPGA with 1417+ user I/O pins available I would be interested to hear it. 
This RISC-V core from Western Digital was demonstrated on an Artix 7 FPGA, so my assumption is that it could fit on an Arria 10 and that it doesn't actually require 1417 I/O pins. I guess their top-level wrapper needs a higher level wrapper istelf. Or perhaps their compilation flow has some way of excluding a subset of ports from needing to reach physical I/O. 
Any example of a RISC-V soft core operating on an Arria 10 would be extremely helpful.

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How to mitigate excessive I/O pins fitter error

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