Thanks for being a part of WWDC25!

How did we do? We’d love to know your thoughts on this year’s conference. Take the survey here

Thunderbolt PCIe 4-devices by daisy chain connection problem

Hello everyone

I have been developing PCIe device driver through Thunderbolt. However, it was confirmed that up to three devices connected to the daisy chain worked normally, but the fourth device failed to operate the _CopyDeviceMemoryWithIndex() function for connection with the BAR0 App and did not work properly. The standard specification of Thunderbolt 3/4 is said to be supported by daisy chain connection up to 6 units, but in reality, it is only 3 units, so I ask the forum for technical confirmation. Of course total 4 device by 2-port x 2-device daisy chain connecting has working well. And the PCI entry in System information app indicates that all devices have normal load of the PCIe device driver.

I'll be answering this in your other forum post here.

__
Kevin Elliott
DTS Engineer, CoreOS/Hardware

Thunderbolt PCIe 4-devices by daisy chain connection problem
 
 
Q