iMac m3 thunderbolt speed?

[mogens]

The iMac M1 is thunderbolt 3, has this changed to thunderbolt 4 on the new M3?

 

[PaulD-UK]

No. This is Apple's description:

Two Thunderbolt / USB 4 ports with support for:

• DisplayPort
• Thunderbolt 3 (up to 40Gb/s)
• USB 4 (up to 40Gb/s)
• USB 3.1 Gen 2 (up to 10Gb/s)

The reason is that the TB4 spec mandates 'two displays' per TB4 port, which Apple doesn't support on the M3.
In all other respects M3 ports give TB4 performance, but they just can't use the name...

 

[mogens]

No. This is Apple's description:

Two Thunderbolt / USB 4 ports with support for:

• DisplayPort
• Thunderbolt 3 (up to 40Gb/s)
• USB 4 (up to 40Gb/s)
• USB 3.1 Gen 2 (up to 10Gb/s)

The reason is that the TB4 spec mandates 'two displays' per TB4 port, which Apple doesn't support on the M3.
In all other respects M3 ports give TB4 performance, but they just can't use the name...

Thanks. I noticed when i connect two TB external TB 3/4 drives to the TB ports on my Imac M1 one of them (the last connected) change to a USB 3.2 connection max. 10GB/s. But I guess that TB4 won't change that?

 

[chrfr]

Thanks. I noticed when i connect two TB external TB 3/4 drives to the TB ports on my Imac M1 one of them (the last connected) change to a USB 3.2 connection max. 10GB/s. But I guess that TB4 won't change that?

Are you connecting each disk to a separate port or are they in a hub or other connection? Each Thunderbolt port on all Apple Silicon Macs so far are on separate buses so connecting 1 disk should not affect the other's connection speed. This isn't a typical behavior so I'd start by looking at your enclosures and cables.

 

[mogens]

Are you connecting each disk to a separate port or are they in a hub or other connection? Each Thunderbolt port on all Apple Silicon Macs so far are on separate buses so connecting 1 disk should not affect the other's connection speed. This isn't a typical behavior so I'd start by looking at your enclosures and cables.

I’m using both ports.
Interesting. it’s a acasis tbu 405 and a jeyi 2464 pro. The jeyi is a USB 4 enclosure, and I get faster speeds with the same ssd (sn 850x). I don’t have two “pure” TB enclosures, so I can’t try that.

 

[PaulD-UK]

It comes down to the TB port’s inability to supply the high power needs of Acasis/Jeyi bus power SSDs.
These enclosures used more power than Apple has provided, so the last drive connected reverts to USB mode which uses less power.

 

[mogens]

It comes down to the TB port’s inability to supply the high power needs of Acasis/Jeyi bus power SSDs.
These enclosures used more power than Apple has provided, so the last drive connected reverts to USB mode which uses less power.

Sounds right. So I’ll need a powered TB hub to make this work.