ASM2464PD Firmware

Open-source C firmware for the ASM2464PD USB4/Thunderbolt to NVMe bridge controller.

Build and flash the firmware for tinygrad with

make -C handmade flash

Source is at handmade/src/main.c it's short and readable

There's a 0xF0 control message that reads/writes PCIe TLPs that gets 3.6 MB/s write, 1.8 MB/s read. This is slow, but it can read and write anywhere on the PCIe BAR.

There's a 0xF2 DMA message that reads/writes to the 512 kB SRAM on the ASM chip. It gets 700 MB/s read+write on 10 Gbps USB3. It is accessible on the PCIe BAR at 0x200000. The SRAM read needs a write from the PCIe device side at 0x822000 to trigger the read. You can see an example of this working / speed test with pcie/test_sram_verify.py

See CLAUDE.md for more stuff like how to run the emulator.