Maximum frequency obtained when synthesizing the RI5CY core multiplier with 28 FD-SOI
#1
Hello,

Out of curiosity, I'm learning more about the RI5CY core, especially the ex_stage. I read the Near-Threshold RISC-VCore With DSP Extensions for Scalable IoT Endpoint Devices paper and I got the core from the dedicated github page. Using Synopsys Design Compiler and the 28nm FD-SOI technology (the only technology available to me), I synthesized the multiplier (mult.sv) present in the RI5CY core. I obtain a maximum operating frequency of the multiplier of 200 MHz.

This frequency seems to me a little low. Considering the various documents I have seen on the internet, I would expect to obtain a frequency rather between 450 and 650 MHz.

Does anyone know if the maximum frequency of 200MHz is actually too low for the RI5CY core multiplier?


Thank you in advance.
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#2
STM28 FDSOI has many corners and flavors. It also depends a little bit on them. Unfortunately, NDAs would not allow me to comment on specific speed, but you are right the number is low from what you expect, it could be a lower power, lower leakage setup.

Also note that synthesis constraints can result in different implementations that exploit different trade-offs. Make sure your timing constraints and also putput loads are specified properly
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