u/DarthOninoko

Hi there,

I'm new here, but I've been reading posts about FPGA design for a while, and they inspired me to start the project I'd like to show you today.

Kromi One - In its original form

I'm building Kromi One, a new home computer around the AMD Kria K26. Its chipset, Aura, runs in the PL and draws Full HD at 60 fps today on a KV260. I wanted to share how it's built and get your take.

Keeping old Amiga tradition, I gave some FPGA elements names.

Drawing (Klara):
Works on 64 × 64 tiles held on chip; a batch mode applies many commands to a tile and writes it once. Plain blits run at 16 px/clk, affine ones (any 2 × 3 matrix, bilinear filtering, texture wrap) at 4 px/clk. There's a programmable combiner in the spirit of the GameCube's TEV (LERP, compare, min, max, DOT3). One stage is built; the interface allows four. Ten full-screen blended layers plus a fill hold 60 Hz, about 1.4 Gpixel/s.

Display (Dora):
A base plane plus four planes composed during scan-out at 1 px/clk, then a 17³ 3D LUT (.cube grid, trilinear), then a ×1 to ×4 scaler chosen per frame: nearest, bilinear or AMD FSR 1 (EASU + RCAS), matched bit for bit against an integer reference. Planes cost the drawing engine about 2 %; one scene went from 21.3 ms with engine-drawn layers to 10.4 ms with planes.

Memory (no fancy name here 😄):
4 GB DDR4 shared with the A53s. The PL gets over 12 GB/s on long sequential transfers. The display has its own port, its own priority class and a 32 KiB buffer: zero underflows with 9 to 11 GB/s of PL load plus CPU copies.

A C reference renderer decides every byte. The QEMU model, the RTL simulation and the board must all match it exactly. The board latches a CRC-32 of every output frame, which is read back and compared with host-computed CRCs: 432,009 of 432,009 frames were exact in a two-hour run. Mutation tests make sure deliberately broken RTL gets caught.

Programs never touch registers. They submit 128-byte command records into rings, and the firmware validates each one in under a microsecond before the chipset sees it.

Next up is textured triangles (FuryGpu showed what the K26 can do there). I'd love to hear from anyone who has done perspective-correct texturing in fabric on the K26 or similar parts. What throughput did you get, and what would you do differently?

The full write-up, my very first blog post on a brand-new site, compares it with MiSTer, the MEGA65 and others: https://kromi.one/blog/remake-or-new-machine/