RealTek RTS5490 USB4 hub controller port analysis

goldenstateservicesj
Jun 5, 2023
2 min read

[Update: First RTS5490 dock launched – full review and teardown]

[Updated 2023/06/07 with table comparing chipsets]

Introduction

At Computex Taipei 2023, there were many product announcements. One that piqued my interest was the previously unannounced RealTek RTS5490, a USB4 hub controller chip intended for docking stations.

Here are the specs provided by Realtek at the Computex booth:

Interface : Type-C / USB 4 / TBT3 / USB 3.2 / DP2.1
Type-C V2.2 and USB Power Delivery 3.2 (240W capable)
USB 4.0 Gen3x2 (up to 40Gbps)
Thunderbolt-3 Gen3x2 (up to 40.625Gbps)
USB 3.2 Gen2x2 (up to 20Gbps)
Supports DisplayPort 2.1 Alt Mode
Built-in DP2.1 TX and RX Port (up to UHBR20 80Gbps)
Built-in USB 2.0 Hub Controller

While helpful, this only really tells the upstream story. But there was a PowerPoint running on a PC in the demo booth showing a few more details:

RealTek Computex 2023 PowerPoint presentation

So we can see the following features:

UFP: USB4 40Gbps bi-directional link to host PC (or 80Gb/s DP 2.1 for single direction)
DFP1/DFP2: 40Gb/s USB4 downstream links (or 80Gb/s DP 2.1 alt mode)
DFP3/DFP4: USB 3.2 Gen2x2 20Gb/s links
1x DP 2.1 80Gb/s output
1x DP 2.1 80Gb/s input

I reckon this chip can function in a few different modes depending on the firmware:

3-way DP 2.1 8K MST hub
USB4 hub with DP 2.1 output, 2x USB4 ports, and 2x USB 3.2 Gen2x2 ports

A curious feature is including both a DP 2.1 output and an input. On the PCB we see confirmation of this as there are 8 highspeed differential pairs between the RTS5490 and the RTD2188 3-way MST chip. I’m not sure what the purpose of this is. Perhaps in this demo, the RTD2188 is doing some manipulation of the DisplayPort data to compress, decompress, encrypt, decrypt, convert color spaces, extract MST streams, or some other feature that isn’t built into the RTS4590. Or perhaps the extra input could be used to somehow make a KVM solution with two host PCs connected or inter-domain data or display-stream sharing?

8 differential pairs between RTS5490 and RTD2188

Also curious is Realtek’s inclusion of two Gen2x2 20Gb/s downstream ports – a port spec that has low market adoption in 2023 compared to 40Gb/s Thunderbolt and 10Gb/s USB. These ports are probably intended to be used with Realtek’s new RTL9220 SSD controller, the ASM2364 SSD controller or similar devices rather than be exposed as external USB-C ports.

In any case, the RTS5490 is an exciting addition to the market and excellent competition for the Intel JHL8440 and Via VL830 chips.