USB4 SSD not detected when connected directly to M4 MacBook Pro

[Ber92]

Hello,

About 4 months ago I bought a brand new 2024 M4 MacBook Pro. I also just received a new Corsair EX400U USB4 SSD to backup my files from my old Windows PC.

The Macbook Pro, however, doesn't detect the SSD when I connect it using the included USB4 compatible cable. It doesn't show up on disk utility. I tried all 3 USB C ports to no avail.

Corsair says it is compatible with MacOS 13 and later versions.

The drive works, using the same included USB cable, with my IPhone 15 Pro, my old Windows 7 PC, and with my work issued Dell Precision 5570 with USB C ports that support Thunderbolt 4 / USB4. I am not sure if it was in USB4 mode on the 5570.

I tried to connect it using a borrowed Dell DA305 USB-C mobile adapter and it worked. I was able to access the files that I backed-up.

I have managed to get the system logs when I connect the SSD (without the USB Hub) using this command :
"log stream --predicate 'eventMessage contains "USB" OR eventMessage contains "Thunderbolt"' --info"
They are in text file attached to this post.

Any insight will much welcomed and appreciated.

(Sorry if I chose the wrong section of the forum to post this, I am new here)

 

[MayflyMaven]

I would check System Settings > Privacy & Security > (scroll to the bottom) Security: Accessories. Even at the "highest" security ("Always ask") it should be prompting you to allow the accessory. I'd at least temporarily try "Always allow", then detach/reattach the device to see if it shows up.

 

[DeltaMac]

Do you have any other USB devices that you could try, maybe a flash drive?

 

[bogdanw]

There is one error that might suggest it requires additional power. Have you tried to have your MacBook plugged in to power while connecting the EX400U directly?

"2025-08-12 22:13:25.374593+0200 0x464c7        Error              0x0                                    0            0        kernel: (AppleTypeCPhy) AppleT8132TypeCPhy@3: AppleTypeCPhy:pen: owner AppleT8132USBXHCI type 2 options 0x00040000 completed with 0xe00002d6
2025-08-12 22:13:25.374601+0200 0x464c7        Default          0x0                                    0            0        kernel: (AppleSynopsysUSB40XHCI) AppleT8132USBXHCI@03000000: AppleT8132USBXHCI::setUSB3Mode: setPowerLevel or open failed with 0xe00002d6"

 

[Fishrrman]

Re the "power issue" bogdan mentions above...

Do you have a POWERED USB hub around (even if it's not USB4)...?
If so, could you set that up, plug the drive into the hub, and see if it then shows up on the desktop?

 

[Ber92]

Thanks everyone for the responses.

I tried the accessories security always allow setting, no change.
I used my regular 32GB USB Flash drive with the macbook and it worked with no issues.

Regarding the power theory, I think it is unlikely to be the issue. I should probably clarify something in my original post : when I connected the SSD to the Macbook Pro through the DA305 USB C adapter, it did show up on the desktop and I was able to access its content. This USB adapter doesn't require dedicated a power supply.

Some might think "well there you go, problem solved..." Well for me know no, it isn't. I bought this, almost $2000 macbook PRO for the IO and I don't plan on carrying dongles and adapters along with it. If I have to, I will also carry some bitterness from the feeling that I have been and deceived by either manufacturers.

I used ChatGPT to see it can find anything in the system logs, here is the response :

I went through your USB connection logs, and here’s the key takeaway: Your Mac detects a device connection on Port-USB-C@4 and negotiates USB 3 Gen 2 (10 Gbps) at first. Then we see driver status errors like: AppleTypeCPhy:pen ... completed with 0xe00002d6 AppleT8132USBXHCI::setUSB3Mode ... open failed with 0xe00002d6 That 0xe00002d6 is an I/O kit “device not responding” error — the controller can’t establish stable comms in the negotiated mode. After repeated USB2/USB3 mode changes and re-registrations, macOS eventually removes the transport and doesn’t mount the drive. Interpretation: Your Mac is trying to bring up the link in high-speed mode (USB4/USB3 Gen 2), failing the handshake, and giving up. This is consistent with a USB4 controller compatibility issue or bad fallback handling. When you use your USB hub, it forces a simpler USB mode that avoids the failing negotiation — which is why it works.

So.... I don't know.

One one hand, I am wondering if the EX400U is the issue, but :
- It works with the IPhone 15 Pro, albeit in USB 3.2 mode, since that highest speed the IPhone's USB port can support.
- It works through a USB multiport adapter with the Macbook, I am pretty sure in USB 3.X mode also.
- Corsair says, on every document and marketing material related to this product : it is compatible with Macbooks

On the other hand, is it a Macbook issue ? Well I tried to connect a Dell TB16 Thunderbolt dock to it and I got an error dialogue window. The Macbook doesn't seem to support it either.

Sigh.

 

[BrianBaughn]

If it doesn't connect to another current MacBook Pro then I'd say the seller isn't quite correct.

 

[MacCheetah3]

The drive works, using the same included USB cable, with my IPhone 15 Pro, my old Windows 7 PC, and with my work issued Dell Precision 5570 with USB C ports that support Thunderbolt 4 / USB4. I am not sure if it was in USB4 mode on the 5570.

I tried to connect it using a borrowed Dell DA305 USB-C mobile adapter and it worked. I was able to access the files that I backed-up.

Interpretation: Your Mac is trying to bring up the link in high-speed mode (USB4/USB3 Gen 2), failing the handshake, and giving up. This is consistent with a USB4 controller compatibility issue or bad fallback handling. When you use your USB hub, it forces a simpler USB mode that avoids the failing negotiation — which is why it works.

So.... I don't know.

One one hand, I am wondering if the EX400U is the issue, but :
- It works with the IPhone 15 Pro, albeit in USB 3.2 mode, since that highest speed the IPhone's USB port can support.
- It works through a USB multiport adapter with the Macbook, I am pretty sure in USB 3.X mode also.
- Corsair says, on every document and marketing material related to this product : it is compatible with Macbooks
View attachment 2537179

On the other hand, is it a Macbook issue ? Well I tried to connect a Dell TB16 Thunderbolt dock to it and I got an error dialogue window. The Macbook doesn't seem to support it either.

Sigh.

Have you tried another USB-C to USB-C, not just the original cable with an adapter?

 

[bogdanw]

Regarding the power theory, I think it is unlikely to be the issue. I should probably clarify something in my original post : when I connected the SSD to the Macbook Pro through the DA305 USB C adapter, it did show up on the desktop and I was able to access its content. This USB adapter doesn't require dedicated a power supply.

Because it downgrades the connection to USB 3 (USB-A 3.2 Gen 2).
When you connect it directly it should work at maximum USB4 speeds (40Gbps), that might require more power.

 

[Fishrrman]

The Corsair drive page says support for both USB4 and thunderbolt4.

Have you tried a thunderbolt 4 cable with it?
If not, I suggest you obtain one, and give that a try.

 

[okkibs]

The enclosure Phison chipset isn't compatible with the M4 Macs in USB4 40Gbps mode. It works through hubs because as someone already stated this switches it to a different downgraded slower USB mode. If you don't need the full 40Gbps mode you can get a different USB cable that simply doesn't support 40Gbps and it will force a downgraded connection without needing a hub in between.

The alternative is to return this expensive garbage to Corsair and let them know they should put a disclaimer on their website and test their products with the devices they're supposedly compatible with. As far as I can see they don't offer a guarantee that it works with M4 Macs specifically instead merely claiming that it works on all Macs.

It's the typical thing to state when they haven't tested with any particular machine. M4 Macs and this enclosure were released at roughly the same time so perhaps Corsair didn't even have a M4 Mac available at the time of testing and merely assumed compatibility.

Compatible with any Mac is a wild statement since Corsair has absolutely no way to ensure their product will work with future Macs that don't exist yet. How could Corsair possibly guarantee that it works with hardware that doesn't yet exist on the market? And what would they do if years down the road one of their products ended up becoming incompatible, would they refund the customer? I highly doubt it.

Now you could assign part of the blame to Apple because we know Apple's USB-C ports are picky what devices and chipsets they accept. But ultimately it's Corsair that incorrectly claim Mac compatibility.

There are other 40Gbps NVMe enclosures available that actually work and 40Gbps external SSDs are sold by Samsung and others and these work as well. So clearly the Macbooks do support 40Gbps. The catch is that these working devices have an Intel chipset instead of the incompatible Phison. I think there is a compatible Asmedia chipset as well.

By the way I am a fan of Corsair hardware and have a lot of it and Corsair makes quality products. My complaint is merely towards their marketing that makes impossible universal compatibility claims. Or it's simply an error on their website. But the end result is the same that the enclosure doesn't do what it promises and the customer ends up with a headache.

I know Corsair is participating in this forum in some capacity so perhaps they end up seeing this and can find an employee with a 14"" M4 MBP (not M4 Pro/Max!) and verify that their enclosure indeed won't work with the included 40Gbps cable.

 

[MacCheetah3]

The enclosure Phison chipset isn't compatible with the M4 Macs in USB4 40Gbps mode.

I had a difficulty finding anything about that chipset. I did come across a comment/note about no general/univeral firmware variant, each OEM must develop and support their own version(s). So, it appears, the problem is up to Corsair to resolve.

I think there is a compatible Asmedia chipset as well.

USB Controller|ASMedia Technology Inc.

ASMedia Technology was founded in 2004 and went public in 2012 (stock code: 5269.TW). Headquarter is located in Taiwan. ASMedia specializes in high-speed interface technologies with strong expertise in high-speed SERDES in house development. Company strives for continual innovation and the...

www.asmedia.com.tw

And that’s indeed compatible with M4. The OWC 1M2 utilizes the ASM2464 and I have another no-name, sell as many as we can then discontinue USB4 enclosure that also features the Asmedia. They work well, that is, if you don’t connect too many.

By the way I am a fan of Corsair hardware and have a lot of it and Corsair makes quality products. My complaint is merely towards their marketing that makes impossible universal compatibility claims. Or it's simply an error on their website. But the end result is the same that the enclosure doesn't do what it promises and the customer ends up with a headache.

IMO… Eh… On average, their products are okay. I have an older Origin PC prebuilt — long story — but their, Corsair and Origin branded, recent models have gotten plenty of flack.

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[bogdanw]

I had a difficulty finding anything about that chipset.

"The Corsair EX400U ... contains the Phison PS2251-21 40Gbps USB4 portable SSD controller with KIOXIA TLC memory."
https://www.thessdreview.com/hardware/portable-ssds/corsair-ex400u-usb4-external-ssd-review/
PHISON Electronics Corp. - PS2251-21 (U21)
"Interface: USB4 (40 Gbps), USB 3.2 Gen2x2 (20 Gbps), USB 3.2
Gen2x1 (10 Gbps), USB 3.2 Gen1 (5 Gbps), USB 2.0 (480 Mbps)"
https://www.phison.com/en/u21
https://www.phison.com/images/image/ProductBrochure_Consumer_PS2251-21_070325.pdf