I have a Sandisk USB-C/Thunderbolt 4 SSD connected to my 2020 MacBook Pro 13". The SSD supposedly reaches a read/write of 1000MBps. Using Black Magic to test, it's only achieving 300-350. Is that right?
Got a tip for us?
Let us know
Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
SSD Speed
- Thread starter dazzer21-2
- Start date
- Sort by reaction score
How fast is the TB 4 port? About 40 Gbps. You can divide that by 10 to estimate real-word BYTES per second. So, about 4,000MBps.
How fast is USB-C? This depend on is the poert is a new USB 3.2 or an older one. So USB-C is either 10 Gbps or 5Gbps. If it is 5 Gpbs then about 500 Giga BYTES per second is about right. But there is some overhead so you don't get the full port speed.
You have to post more details about the drive.
Last edited:
This is an area where capitalization, calculation, and real-world measurements all collide. The net of it is that the 40Gbit/s USB4/Thunderbolt offers NVMe drive performance that caps at (round numbers) ~3000MByte/s for a variety of reasons. It's not a simple story, so I won't attempt to tell that here...there are long threads about this specific topic.
Secondly, USB protocol (on the USB-C connector) is available at 5Gbit/s and 10Gbit/s. The 5Gbit/s USB connections are capable of ~400MByte/s of SSD throughput. Again, there are ranges and explanations if you want to know the details.
Here are things to keep in mind when evaluating serial links between a computer and an SSD:
1- The relationship of bits to bytes is the same as pints to gallons. (8:1)
2- All serial links have encoding strategies that dilute the throughput (e.g. 8b/10b or 64b/66b or 128b/132b, etc.)
3- Protocol overhead, link arbitration, and protocol segmenting will all reduce the net throughput
Secondly, USB protocol (on the USB-C connector) is available at 5Gbit/s and 10Gbit/s. The 5Gbit/s USB connections are capable of ~400MByte/s of SSD throughput. Again, there are ranges and explanations if you want to know the details.
Here are things to keep in mind when evaluating serial links between a computer and an SSD:
1- The relationship of bits to bytes is the same as pints to gallons. (8:1)
2- All serial links have encoding strategies that dilute the throughput (e.g. 8b/10b or 64b/66b or 128b/132b, etc.)
3- Protocol overhead, link arbitration, and protocol segmenting will all reduce the net throughput
Look in System Information.app. Is the drive connected as USB or Thunderbolt/PCIe?
- Look in the USB tab for USB devices. Check the USB connection speed of the USB device and any parent USB hubs.
- Look in the Thunderbolt tab for Thunderbolt devices.
- Look in the PCIe tab for PCIe devices (NVMe) that are connected using Thunderbolt.
A Thunderbolt device should be able to do up to 2500 MB/s.
A USB 10 Gbps device should be able to do 1060 MB/s (or slightly less when using USB controller of Apple Silicon Macs)
A USB 5 Gbps device should be able to do 450 MB/s (or slightly less when using USB controller of Apple Silicon Macs)
It seems like the device might be connecting as USB 5 Gbps in your situation because Apple Silicon Thunderbolt ports are not as good as Intel Thunderbolt ports. https://forums.macrumors.com/thread...ally-10gb-s-also-definitely-not-usb4.2269777/
To get USB 10 Gbps, you may need to insert a USB 10 Gbps hub or Thunderbolt dock/hub.
To get Thunderbolt PCIe speed, you may need to insert a Thunderbolt dock/hub.
Thunderbolt 3 dock/hub might be best to avoid USB tunnelling with Apple Silicon Mac's USB controller. You can avoid USB tunnelling to a Thunderbolt 4 dock/hub if there's a Thunderbolt 3 device between the Apple Silicon Mac and the Thunderbolt 4 dock/hub.
- Look in the USB tab for USB devices. Check the USB connection speed of the USB device and any parent USB hubs.
- Look in the Thunderbolt tab for Thunderbolt devices.
- Look in the PCIe tab for PCIe devices (NVMe) that are connected using Thunderbolt.
A Thunderbolt device should be able to do up to 2500 MB/s.
A USB 10 Gbps device should be able to do 1060 MB/s (or slightly less when using USB controller of Apple Silicon Macs)
A USB 5 Gbps device should be able to do 450 MB/s (or slightly less when using USB controller of Apple Silicon Macs)
It seems like the device might be connecting as USB 5 Gbps in your situation because Apple Silicon Thunderbolt ports are not as good as Intel Thunderbolt ports. https://forums.macrumors.com/thread...ally-10gb-s-also-definitely-not-usb4.2269777/
To get USB 10 Gbps, you may need to insert a USB 10 Gbps hub or Thunderbolt dock/hub.
To get Thunderbolt PCIe speed, you may need to insert a Thunderbolt dock/hub.
Thunderbolt 3 dock/hub might be best to avoid USB tunnelling with Apple Silicon Mac's USB controller. You can avoid USB tunnelling to a Thunderbolt 4 dock/hub if there's a Thunderbolt 3 device between the Apple Silicon Mac and the Thunderbolt 4 dock/hub.