PCIe x4 adapter with USB 3.1 ports, one type C and one type A

The card has a USB type C port (socket) for use with new devices and a USB 3.1 type A port for use with older devices. The main chip is an ASM1142 chip for use with USB 3.1 ports. There is also an ASM1543 chip to handle USB 3.1 type C ports and spread the heat generated by the high power supplied to some USB devices.

Tested on small, a computer with a spare PCIe x4 slot and USB 3.0 ports.


10 Gbps

USB 3.1 runs up to 10 Gbps, 10 Gigabits per second. Note that is bits per second, not Bytes per second. In an ideal world, you get GBps, GigaBytes per second, by dividing Gbps by 8 as there are 8 bits in a byte. The theoretical result is 1.25 GBps. In most cases the computer reports bytes of data transferred and the data bytes are surrounded with control data. A more accurate estimate is to divide Gbps by 10. This gives us either 1 GBps. Real benchmarks reach 0.9 GBps, 900 Mbps, about twice the maximum speeds you see with USB 3.0.

Tests of read speeds with SSDs are easy because the top of the line NVMe M.2 SSDs have read speeds faster than USB 3.1. Write speed tests are more difficult because only the most expensive SSDs can accept writes faster than USB 3.1. There may be a short burst of fast writes while the SSD fills up a buffer but long writes, perhaps a video file, soon slow down to less than the maximum USB 3.1 speed.

You can use a couple of fast SSDs in a RAID 1 configuration to test write speeds. I do not have the SSDs or RAID hardware to test that. The RAID device is also a limitation and the RAID configuration is also a limitation.


The ASMedia chips on the adapter card handle a USB 3.1 port, a genuine 10 Gbps USB 3.1 "Gen 2" port, not a fake USB 3.1 "Gen 1" port. To get the maximum speed, the adapter has to be plugged into a PCIe x2 slot of Gen 2 or better. I am testing in a PCIe x4 slot and will use only one port at a time.

Every other component has to be compatible with 10 Gbps, the cable, the SSD, the chips in the SSD enclosure, and the computer running the tests. My test machine has run an SSD faster than 10 Gbps.

The extra power socket on the top right hand corner is there to supply extra power for the USB ports when the attached devices draw the full amount of power available through USB 3 and USB 3.1 ports.


This is the chip your computer sees. Your operating system needs a driver, or equivalent, to talk with this chip. The chip appears as a USB host and will present two USB ports when they are in use. The chip appears to connect direct with the type A port and the ASM1543 chip instead of the type C port. The ASM1543 chip handles some of the type C logic. The ASM1543 chip probably also helps spread out the power load when the type C port is used at full power.

Here is a description of the chip from the ASMedia Web site.

ASM1142 is an ASMedia first Universal Serial Bus 3.1 host controller, compliant with Intel eXtensible Hot Controller Interface specification revision 1.1, bridging PCI Express interface to two ports of USB3.1, up to 10Gbps high speed bandwidth, backward compatible with legacy USB function and devices. It can configure PCI Express as Gen2x2 or Gen3x1, compliant with USB Attach SCSI Protocol revision 1.0, supporting the functions of debugport.
ASM1142 integrates ASMedia self-designed PCI Express/USB 3.1 PHY, and it also integrates two internal regulators to supply normal core power and suspend core power, supporting the driver on Windows 7, Windows 8.0, Windows 8.1 and various Linux Kernels. The application of ASM1142 includes Motherboard, Desktop PC, Notebooks, Workstations, Servers, Add-in card, PCI Express based embedded platform.


The ASM1543 chip handles a USB 3.1 type C port. The chip detects the way the plug is inserted and handles some other tasks. Using a separate chip would also spread out the heat generated by a USB 3.1 port running at full power. The chip will probably run hot when you draw the maximum power from the USB port.


The device works as a USB 3/3.1 port. The type C port handles the new plug/socket format.