Offsite: USB4/TB4 from scratch?

Tldr:
The goal. A USB/ Thunderbolt 3-4 controller will full 127 device 256 endpoint support.
To be installed on a PCIe or M2 card and connected via single thunderbolt 3 port on a pre-Mchip Mac and/or M series Mac.


Hello friends.
I’m seeking help. I’ve hit a dead end.
Like many in both programming and tinkering with rapid file turnover, I prefer small fast SSDs in JBOD (just a bunch of discs) over large drives in raid where I’m bound to kill whole drives quickly.

Currently I have a few dozen USB 3.x internal Samsung drives connected via Sabrent SATA->USB3 adaptors To hubs.

The hubs range from 8-12 ports and are well documented rebranded open spec devices.
I’m currently suffering Drive dropout. And now having lost two drives due to B-tree corruption, a disk copy was in progress, I’ve lost every project starting with the letter H until I can get help doing a binary rebuild.


What I know:
Each hub controller limits the endpoints to 5 per port.
Eg: 10 ports, 10 devices, 50 endpoints.
Each controller in the iMac is limited below max spec. Each controller runs two ports. There are two dedicated to USB3 and one unlimited one running USB and Thunderbolt 3 ports.

The problem: i can not find the endpoint use for either Samsung drives (evo/qvo) nor the apple iMac controllers.
I figured out the issue is an endpoint overflow. But I can’t figure out the cause. I know the problem is the controllers in my iMac (2016v late 2017 release). But I can’t get an accurate idea of what the controller limits are.

The project.
Assuming no one here has a better idea for my use case.

I want to build a hub for hubs. Probably running m64 (a streamlined version of True64 Unix). And connect each USB hub to an independent controller via USB3.x using USBc ports.
The super hub would then control data transmission to share 2 USB3 ports and 1 Thunderbolt 3 port on my iMac.
A modern variation of time sharing.

Again, unless someone has a better idea.
I’ve heard rumours that the LC JBIG disk towers play well with TB3 and TB4 hubs.
But the 8 bay units available today run $300-$400 each. And I can’t find anyone who has actually tried plugging 4 or 5 into a TB hub. Then to a Mac OR pc.
Though I’ve seen two connected to a dual controller MacBook Pro.

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So, here’s my final method of solution.

I purchased an extra ACASIS 12 port USB3 hub. And a spare OWC thunder bay.

The ACASIS has two USB 4 controllers in it based on the last unfinalised draft spec. It’s also properly self powered. So I took the hub apart. I removed the B I/o port and hard wired a USB4 to SATA adaptor board to the end.
Then ran a quad-SAS breakout cable from the hub connector into one of the SATA bays through a small cut hole in the front grill of the TBay.
I now have 127 device support per bay in the 8 bay storage cage if I wish to repeat it.
It doesn’t solve the drives-on-the-table aspect. But it cleans up the process considerably.

It was surprisingly easy. Both the thunderbay and the hub have high quality full features controllers.

Another surprise is the ACASIS has a full micro netBSD rom in the ASIC!
Using Fuse with fluX on MacOS I was able to tunnel commands directly to the ASIC!
A generally useless but unexpected twist! The only change I made was completely disabling low power support.


The ultimate end of this was a bit of strange knowledge. Finding a modern USB hub using a microprocessor more powerful than most 90s high end servers. Running a late 90s operating system.
All in a long rectangular box the length of a CDRom drive!

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