USB-to-Ethernet Controllers: DAVICOM DM9601 vs DM9621 (USB 1.1 vs USB 2.0 Is the Key)
A USB-to-Ethernet controller turns a host that has a USB port but no Ethernet MAC into a standard NIC via a driver. The DM9601 and DM9621 are both 10/100 on the Ethernet side; the difference is USB — DM9601 is USB 1.1 (12Mbps, can’t fill 100Mbps) while DM9621 is USB 2.0 (480Mbps). This guide shows how to choose and contrasts SPI (DM9051) and MAC+PHY approaches.
What is USB-to-Ethernet, and when to use it
A USB-to-Ethernet controller is a USB device that integrates the 10/100 Ethernet MAC and PHY on one chip; plugged into the host’s USB port, the host’s USB-networking driver presents it as a standard NIC (ethX on Linux). Its use is clear: when your SoC / single-board computer has no Ethernet MAC of its own but does have a spare USB host port, and you want to add wired networking the “driver makes it a NIC, minimal glue logic” way, you use one. DAVICOM’s DM9601 and DM9621 are exactly such chips.
DM9601 (USB 1.1) vs DM9621 (USB 2.0)
Both parts are 10/100 on the Ethernet side; the real difference is the USB side: the DM9601 is USB 1.1 Full-Speed, while the DM9621 / DM9621A is USB 2.0 High-Speed (480Mbps, backward-compatible to Full-Speed). The DM9601 is a 2002-era part; the DM9621A is newer (2015 revision) and, besides moving USB up to 2.0, adds TCP/UDP/IPv4 checksum offload, Wake-on-LAN, ARP/NDP offload and 802.3az Energy-Efficient Ethernet (EEE), with built-in packet buffering and an optional RMII interface. So new designs almost always choose the DM9621 / DM9621A.
⚠️ Real throughput: the DM9601’s USB 1.1 bottlenecks
Why is the USB version the key? Because it decides real throughput. The DM9601’s USB 1.1 Full-Speed raw rate is only 12Mbps, and after USB protocol and packet overhead the measured TCP throughput is far below the 100Mbps line rate (in the single-digit Mbps range) — fine for a management port or a low-speed link, but it cannot fill 100Mbps. The DM9621’s USB 2.0 High-Speed gives a 480Mbps channel, well above 100Mbps, enough to approach line rate. So “do you need to fill 100Mbps” directly decides which part to choose. (The actual achievable Mbps varies with host, driver and load — it is a measured value, not a guaranteed spec.)
Drivers: one Linux dm9601 covers all
Driver risk is low. Linux has a single in-tree driver, drivers/net/usb/dm9601.c (config option CONFIG_USB_NET_DM9601), whose USB device-ID table covers the DM9601, DM9620 and DM9621A; plug it in and it usually enumerates automatically as a standard ethX NIC with almost no software development; iPXE and U-Boot also support the DM96xx (friendly to embedded devices that need network boot). Windows drivers are provided by DAVICOM. Overall, the selling point of USB-to-Ethernet is “a mature driver plus minimal glue logic.”
How to choose, and the SPI / MAC+PHY trade-off
Selection flow: first check whether the host has a spare USB host port and lacks an Ethernet MAC — if both, a USB-to-Ethernet bridge is the least-effort solution. Need to fill 100Mbps → choose the DM9621 / DM9621A (USB 2.0); the DM9601 (USB 1.1) only suits a management port, a low-speed link, or keeping a legacy design compatible. New designs should prefer the DM9621A (newer, with offload and power saving, better long-term supply). If your host is not a USB case, weigh the alternatives: an MCU with only SPI → DM9051 (an SPI-interface MAC+PHY); a host that already has an Ethernet MAC → an external PHY is best (best throughput and BOM). JLink Technology is an authorized DAVICOM distributor supplying all three Ethernet approaches — USB (DM9601/DM9621), SPI (DM9051) and PHY (DM9162); tell us your host interface, throughput needs and volumes and we will help with selection and reply with samples, datasheets and pricing.
Products mentioned
DM9601 USB-to-Ethernet Controller
The DM9601 is a DAVICOM single-chip USB-to-10/100M Fast Ethernet controller integrating a USB transceiver (USB 1.1-compliant, works on USB 2.0 host ports), a 10/100 MAC and PHY, and an internal buffer. 3.3V with 5V-tolerant I/O in a 48-pin LQFP — low pin count and low cost, common in USB-to-Ethernet (USB-LAN) adapters and NICs.
DM9621 USB 2.0-to-Ethernet Controller
The DM9621 is a DAVICOM USB 2.0-to-10/100M Fast Ethernet controller integrating an Ethernet MAC and on-chip PHY, an SSRAM packet buffer, and an optional RMII interface. In a 48-pin QFN with auto-negotiation and Auto-MDIX — a low-cost USB network-adapter solution, and the USB 2.0 successor to the (USB 1.1) DM9601.
DM9051 SPI Interface 10/100M Ethernet Controller
DM9051 is a DAVICOM single-chip 10/100M Fast Ethernet controller with an SPI interface, eliminating the need for 8/16-bit parallel bus and greatly simplifying hardware design. Features 16KB SRAM TX/RX buffer, full-duplex flow control, and native Linux kernel driver support — ideal for network expansion on ARM or RISC-V MCU systems.
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