Thunderbolt, USB 3 and gen 2 speeds MacBook Pro, Confused!

[dukeblue219]

One more thing I'll add on the USB vs TB issue, since you asked why USB-connected drives don't use the faster disks if they ARE available. USB drives almost-exclusively use SATA-to-USB adapter chips which are dirt cheap, but limited to SATA speeds and thus SATA drives. True TB drives (which in the case of TB3 use the USB-C connector) can use NVME drives, which are the super fast ones. Why? Because NVME is designed to be interfaced directly into the PCIe bus of the processor. TB3 is (basically) an external PCIe expansion protocol. So, the two work well together.

That's also why you will not find any NVME-to-USB external adapters on the market. If you need to use a random NVME drive (M-keyed drive, PCIe mode only) in an external enclosure you end up buying a $300 TB3 enclosure if you can even find one. Fortunately, some NVME drives that are B&M-keyed support SATA as a fallback and so you can use those cheaper adapters.

It's not that USB drive makers are cheap and using SATA drives. That's just what works with USB right now, even though USB 3.1 is capable of pretty fast speeds.

 

[robodelfy]

One more thing I'll add on the USB vs TB issue, since you asked why USB-connected drives don't use the faster disks if they ARE available. USB drives almost-exclusively use SATA-to-USB adapter chips which are dirt cheap, but limited to SATA speeds and thus SATA drives. True TB drives (which in the case of TB3 use the USB-C connector) can use NVME drives, which are the super fast ones. Why? Because NVME is designed to be interfaced directly into the PCIe bus of the processor. TB3 is (basically) an external PCIe expansion protocol. So, the two work well together.

That's also why you will not find any NVME-to-USB external adapters on the market. If you need to use a random NVME drive (M-keyed drive, PCIe mode only) in an external enclosure you end up buying a $300 TB3 enclosure if you can even find one. Fortunately, some NVME drives that are B&M-keyed support SATA as a fallback and so you can use those cheaper adapters.

It's not that USB drive makers are cheap and using SATA drives. That's just what works with USB right now, even though USB 3.1 is capable of pretty fast speeds.

Thanks, thats good to know. I've learned a lot from this thread...turns out I was pretty clueless before!

 

[robvas]

That's also why you will not find any NVME-to-USB external adapters on the market. If you need to use a random NVME drive (M-keyed drive, PCIe mode only) in an external enclosure you end up buying a $300 TB3 enclosure if you can even find one. Fortunately, some NVME drives that are B&M-keyed support SATA as a fallback and so you can use those cheaper adapters.

How does the OWC Envoy work? SATA fallback?

https://eshop.macsales.com/item/OWC/MAU3ENPRPCI/

 

[dukeblue219]

How does the OWC Envoy work? SATA fallback?

https://eshop.macsales.com/item/OWC/MAU3ENPRPCI/

Honestly I dont know. Those are a very unique in that they ONLY support the built-in Apple SSDs which are PCIe, but keyed to only fit in Macs. There could be enough of a market that OWC built a bridge between the PCIe drive and USB 3.0 protocol. Or maybe it's a SATA mode thing. I'd be curious to know. Looking at some of the ads, it seems like they're using the standard AsMedia chipset that provides SATA to USB bridging.

Any commercial USB enclosure is going to run SATA speeds and require drives that are SATA capable. If the drive is PCIe-only it will require a true TB connection and those are, as I mentioned, rare and expensive.

If Apple just used off-the-shelf NVME drives this would be a lot simpler, nevermind the whole mess of Thunderbolt using the USB-C connector (which is good, but confusing)