Slower USB on front Mac Studio ports?

Update!

I tested the same Crucial X8 2TB SSD drive on another Mac with a USB-C input and it ran at essentially full speed. Almost 900 MB/s. This was an authorized Apple service place, but not Apple themselves. The service agent suggested I plug the drive into the front of the Studio with no other things plugged into any other USB port, including the USB-A ports on the back. I did that and lo and behold, the X8 ran at full speed.

I then plugged my USB-A external hard drive in the back (8TB Western Digital Time Machine drive) and now the X8 would only run at about 500 GB/s again. I tried unplugging my 8TB HD and plugging in my USB-A hub (printers, scanner...) and again, slower speed on the X8. So it seems that plugging anything at all into any other USB port slows down the X8 SSD. Is this normal behaviour?

The fix is to use the rear Thunderbolt port, even though it's a USB drive, but I also want to know if this represents any kind of hardware fault while the Mac is still under warranty. The agent said he would be willing to swap out the whole motherboard, but I really don't want to bother with that unless I know it needs to be done. Is it normal for the USB ports to slow down when anything else is on the same controller? This assumes the USB-A ports are on the same controller as the front USB-C, which it seems it might be.

den.thed wrote:

I’m guessing, it’s something to do the cable.

I would contact Crucial support and/or test the drive on a different USB-C cable.

Nope. Tried a different cable. Same results.

It shouldn't be though. The USB C port is capable of 10 GB/s which is fast enough for 900 MB/s. The Thunderbolt port will only be faster for a drive using a Thunderbolt drive, but it shouldn't be any faster for USB C.

When it's plugged into the back, it says 10 GB/s and when it's plugged into the front... it also says 10 GB/s, but it continues to read and write on the front at about only 520 MB/s compared to over 900 on the back. I don't get it. 🫤. Is there something about the Crucial X8 which does not work fully with USB 3.1?

If the drive was not able to achieve 900 MB/s, then I would agree, but when I plug the USB-C drive into the rear port, it uses USB-C and gives me 900 MB/s. It's not using the Thunderbolt speed when it's only a USB-C drive, so if the drive achieves 900 on the back, it should on the front as well because USB-C will handle that speed.

lkrupp wrote:

If you have access to a different Mac or PC with a 10Gb/sec port try your drive on it and see what you get.

Tried the drive on my MacBook Air M1 and I got about 720 MB/s speed with the same Crucial X8 drive, so three different speeds depending on the port. That seems odd to me.

Yup, that's what I have been using to check the read write speed. The results change marginally with each pass. Mostly it's consistent.

I'm still looking for an answer as to why the port on the front of the Mac Studio is slower than the rear port and slower than the port on my MacBook Air. It's not because the drive is slow, because if that was the case, it would not achieve over 900 MB/s on the rear port.

Rear port of Mac Studio:

No, nothing else on the front. On the rear, I do have a hub plugged into the USB 2 port. That has loads of USB things plugged in, but most, like printers, scanner, sound hardware... are not in use most of the time.

By the way, I am going to bring the Mac Studio to Apple service on Monday morning to have them check the port. I will report back...