Raspberry Pi 4 NIC Documentation

[JohnDuffy]

Hi

I followed the instructions on an earlier thread about changing the MTU 1500 to 9000 bytes. Using Iperf it can seen that this does indeed improve bandwidth from 930 Mb/s to 980 Mb/s. And, this gave me about 10% improvement on some Linpack benchmarks.

However, some Linpack benchmarks now crash the TCP connection when they previously didn't, making one or more nodes on my 8 x Pi 4 uncontactable. When this happens OpenMPI reports that one or more nodes are no longer contactable, probably due to TCP connection problems.

I have a feeling that changing the RX_BUF_LENGTH in bcmgenet.c from 2048 to 12040 bytes, as suggested in the provious thread, may be overflowing the RX buffer and trashing the network stack.

In the BCM2711 peripherals document there is no mention of the NIC.

Any suggestions where to find more hardware/software information about the Raspberry Pi 4 NIC?

Best regards

[hal8000]

If you look at the product specs the ethernet NIC is 1G so if you're getting a 930Mbps benchmark then that's pretty close to the theoretical maximum of 1000Mbps. There's always about a 5% overhead on any LAN connection anyway, and your connection is only as fast as the weakest link. Don't buy cat 5 or a 100M patch lead if youre using a 1G LAN for example, and make sure your SSD can attain a data transfer rate of over 1Gbps if you want to get best network transfers,.

[JohnDuffy]

Yes, you are right. 930Mb/s is pretty close to 1Gb/s. Thanks for the reply.