Claire Xen  🏳️‍⚧️ 🏳️‍🌈 🧙🏻‍♀️ BLM  🏴 🚩

How do you measure size? Number of LUTs? Is block RAM free?

I'd probably go with number of tiles or possibly config frames on Artix 7, with categories something along line of SLICEL only, SLICEL+SLICEM and "free for all" (DSP+BlockRAM). Figuring out the rules and how to evaluate entries is a large part of the effort I think?

Number of tiles and number of frames are *very* different metrics! A bram column contains 28+128=156 frames and 10 tiles. A logic column contains 36 frames and 50 tiles. So either a bram column is 4x *more* expensive than logic (frames) or 5x *less* expensive (tiles).

Related: In the free-for-all category, have points for "worst abuse of hard IP". Example: using a GP_COUNT8 with count=1 as a R-S FF (RST=R, CLK=S) when you run out of flipflops

What I /think/ I'm after is a RISC-V processor which is small enough that dedicating a whole core/CPU to doing bitbanging I2C or other similar low speed peripheral makes sense. RISC-V because of existing tooling for C programming.

i2c is between 100 kbit/s and 3.2 Mbit/s. You won't be able to bitbang that on a core that takes up to hundreds of cycles for each RISC-V instruction. But you'd probably have performance like that with "an 8-bit CPU running an emulator for RISC-V", as you suggested.

If the 8-bit CPU is running at 100MHz (ops) and 100 ops per instruction that is still 1MHz CPU which feels fast enough to bit bang I2C at 100kbit/s? On the RISC-V - I would actually be fine with any architecture that has mainline GCC support.