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Hi,
I am battling a Synplicity run time issue here.
We're emulating an ASIC across multiple FPGAs. The ASIC is partitioned in such a way that there are two parts to each FPGA design - a CORE part and a PERIPHERY part. The CORE part has the "real" design content while the PERIPHERY part is the "glue". It contains muxing, serialization to send the data out on LVDS channels (and also deserializiation and demux for receive path). CORE operates at a slow clock (4 MHz) while the PERIPHERY has higher speed clocks to achieve muxing, serialization to support 750 MHz LVDS transfers. As you can see, the CORE part is unique for each FPGA while the PERIPHERY part is re-used across FPGAs.
When I compile a single FPGA standalone in Synplicity, synthesis run time is around 2.5 hrs. Quartus run times vary from 2 hours to 8 hours. Now to save on run times, I want to use Quartus incremental flow. Idea is that I synthesize the PERIPHERY part only once and use it for all FPGAs. And synthesise the CORE part individually for each FPGA.
But when I start doing this, I find that the runtimes for building the CORE of FPGA are 2x to 4x in comparison to building the complete FPGA itself. This seems counter-intuitive, we're compiling a smaller design, so we expect better run times. When we're compiling the "CORE", we had to define virtual ports for the connections between CORE and PERIPHERY. The number of such virtual ports is ~5k. So, one theory is that the tool spends so much time mapping these virtual ports to low level Altera primitives. These virtual IOs are unconstrained. Even if we set a false path on them to see if that'd help run times, but it did not.
Thanks for your help.
-Dinesh
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Hi,
how did you split your design in the CORE and PERIPHERY part ? By hand or with the "compile point" feature or with Certify ? Is the sum of used FPGA resources much larger compared with the run of the complete design ? Keep in mind that when you use compile point in SynplifyPro or partitions in Quartus the boundaries are fix. This could increase the design size.
Kind regards
GPK
Honored Contributor
