When Apple launched its first M4 Macs just over a month ago, I was surprised that models with M4 Pro or Max chips offered Thunderbolt 5. Although there are still relatively few computers in use with support for TB5, and a dearth of peripherals, this article summarises early experience with this exotic new bus.

What TB5 peripherals are available?

As far as I’m aware, as of today there’s only one Thunderbolt 5 peripheral shipping in quantity, the Kensington SD5000T5 Thunderbolt 5 Triple Docking Station, with a total of three downstream TB5 ports. I’m just completing a full review of this, due to appear in MacFormat and MacLife magazines early next year.

SSDs have been announced by OWC in its Envoy Ultra, and Sabrent. The first of OWC’s have apparently started to ship, although they aren’t expected to become readily available until the New Year, when Sabrent’s are also expected.

OWC has also announced a TB5 hub, but that’s unlikely to appear until next year.

Several PCs are now available with TB5 support, although that seems to be fiddly to configure in Windows. Among those is the Razer Blade 18, which is even more expensive than a MacBook Pro with an M4 Max.

Other than those, there are lots of expensive TB5 cables, just precious little to connect to the other end.

Multiple displays

Many of those rushing to buy into TB5 are doing so because of its promised support for multiple displays. For example, the Kensington dock claims to support up to three 6K displays at 60 Hz with the M4 Max, and two with the M4 Pro. Although I have been unable to test those combinations, there are already reports that the M4 Max works well with three displays connected direct, but only two of those work when using the Kensington dock.

This has apparently taken Kensington and Apple by surprise, but until this has been addressed, I wouldn’t assume that you’ll be able to use all three displays attached to the dock.

Multiple SSDs

In early 2023, when TB4 hubs were becoming available, I wrote a whole series of articles here analysing their performance with a range of different SSDs. Links to those are given at the end. Those predated OWC’s superb Express 1M2 USB4 enclosure that now offers consistent and reliable performance for Apple silicon Macs, but not Intel models, which unfortunately lack support for USB4.

I have recently been revisiting SSD performance, both directly connected to my Mac mini M4 Pro, and working through the Kensington dock. Although some results are impressive, there are others that shock.

As shown in System Information, this dock connects to the host at 80 Gb/s, and to each USB4 drive at the expected 40 Gb/s.

On the bright side, 1M2 enclosures that return direct read/write speeds of 3.7/3.7 GB/s read almost as fast when attached through the dock, but their write speed drops to 2.3 GB/s, similar to many TB3 SSDs attached directly. You can even connect a USB4 drive to each of the dock’s three TB5 ports to benchmark them simultaneously, and get read/write results of 2.1/2.1 GB/s on each of them. That performance represents the maximum total data transfer capacity, matching claims of 6 GB/s made of TB5 SSDs, and equating to 80 Gb/s in TB5/USB4v2 symmetric mode.

Results from TB3 SSDs are more worrying. An award-winning certified Thunderbolt 3 SSD that achieves 2.9/2.2 GB/s read/write attached direct maintained a good read speed through the dock at 2.8 GB/s, but it almost ground to a halt during the write test, at 422 MB/s, that’s roughly the speed you’d expect from a basic SATA SSD.

You can read similar experiences during early testing of this dock for PC World.

For the time being, TB5 performs well with USB4 and directly connected TB3 SSDs, and the dock is a good solution for those wanting high-speed access to two or three USB4 SSDs in OWC Express 1M2 enclosures. The dock does have serious problems when writing to TB3 SSDs, though, where it may fall far short of expectations. Hopefully these problems will be resolved early next year.

Recommendations

• Although TB5 promises much, initial tests show that it currently has problems meeting that.
• Reports indicate that it may not yet support M4 Max chips driving three 6K displays at 60 Hz from a TB5 dock.
• Performance claimed for TB5 SSDs has not yet been confirmed in independent tests.
• Performance of TB3 SSDs attached to a TB5 dock demonstrates some very poor write speeds.
• Performance of USB4 SSDs attached to a TB5 dock demonstrates better and more consistent results, although their write speed also falls.
• TB5 cables and peripherals are expensive.
• Thunderbolt 5 is still at an experimental stage, and may take some time before it realises its potential.

Thunderbolt performance and TB4 hubs

General hub performance
Write speed throttling
How faster SSDs can impair performance of slower ones
Three SSDs on one hub
Getting best performance from Thunderbolt on Apple silicon Macs: a practical guide

Testing with Stibium

When using the ‘gold standard’ method of testing storage using my free Stibium, you don’t normally need to restart the Mac between write and read speed measurements. This has changed with the Mac mini M4 Pro, at least. If you go straight on to measure read speeds, results will be bogus because of what appears to be extensive caching of the files written during the previous write test. That results in absurdly high read speeds of more than 6 GB/s in most cases. This is surprising, as a total of just over 53 GB of files are written during the full write test, which seems far more than macOS should ever cache successfully!

For these tests on external SSDs, I therefore quit Stibium after measuring write speed, unmount the volume tested, remount it in Disk Utility, and open Stibium again to perform the read tests. This apparently clears caches reliably, and read speeds are consistent and in accord with those expected.

Interests

I bought my own Mac mini M4 Pro, Kensington SD5000T5 Thunderbolt 5 Triple Docking Station, and all the OWC Express 1M2 enclosures and their SSDs, at their regular retail prices. The only product tested here that has been provided by a manufacturer is, rather sadly, the TB3 SSD.