Windows 10: Is my motherboard alergic to USB 3.1 Gen 2?

So, my Gigabyte Aorus X470 has numerous USB 3.0 ports, plus 2 ASMedia 3.1 Gen 2 ports back panel and 1 AMD USB 3.1 Gen 2 port motherboard header. I've attached a back panel adapter to the AMD one, with a single USB C socket. If I attach a portable SSD to any of the 3 Gen 2 ports via a short 30cm cable they all work with pretty good stability and reasonable speed circa 750mbps read/write. What I really want, however, is a 3.1 Gen 2 hub next to the keyboard, which requires a cable of around 1m, and there's the rub. I've tried all 3 ports, half a dozen different cables, and 4 different hub

:)

 

Why is my USB 3.1 gen 2 adapter (USB C Female to USB A Male) causing bottlenecking?

I recently picked up an SSD and enclosure with a built in USB Cable. CrystalDiskMark shows a >500MB/s read speed and >400MB/s write speed with a direct USB C connection to a USB 3.1 gen 2 port, so all good here.

But I also picked up these adaptors from amazon.co.uk to ensure I could connect the drive to more common USB type A ports. These adapters noted that they could handle the 10Gbit speeds of USB 3.1 gen 2, although they do note that when this is the case the "other side" (Type A side) runs at USB 2 speeds. Out of a lack of options I decided to give them a go nonetheless and the claim is true. But it's not as simple as saying "these must really just be USB 2 adaptors with a blue finish".

When using the adapter to connect the drive to a front panel USB 3.1 gen 1 port connected to the USB 3 motherboard header, the speeds are ~300MB/s and 400MB/s read and write respectively. So the adapter can handle high throughput but just can't when used in gen 1 or 2 ports on the IO panel of the motherboard itself. Maybe this is a motherboard issue...

Edit: Just verified this across 2 Desktop systems:

• Rear Motherboard IO (USB 3.1 gen 1 and gen 2) with adapter: ~40BM/s
  R/W
  
• Rear Motherboard USB C with no adapter ~500MB/s R and ~400MB/s W
  (full speed)
  
• Front panel IO connected to motherboard USB 3 header (gen 1) with
  adapter ~200MB/s R ~400MB/s W
  

What am I missing here? I have found only one adapter available that clearly states it has 10Gbit ports at either end but it's pricey so any alternative suggestions are welcome. Notably, it has a significant rectangle shape at the USB C side, maybe this is part of the explanation...? See below:

 

Differences in Gen 2 and Gen 3

I got to thinking since my motherboard has two graphics card (16x) slots, but one is a Gen 2 and the other is a Gen 3, why can't I put my M2 SSD in the Gen 3 and my graphics card in the Gen 2. Wow what a differences in speed. Boot time is nothing now, downloads are simple a thing of the past when I did this. I've attached a picture of the differences between the Gen 2 and Gen 3 speed test.

 

USB 3.2 Gen 1 Type-A Module

Why? They are the same speed. According to the motherboard diagram that socket numbered 9 is usb 3.2 gen 1, which is the same as usb 3.0

USB: Port Types and Speeds Compared | Tripp Lite