First you need to read the surperb reviews of both boards done by Steven Bassiri at Tweaktown. I asked him why he increased the quality rating from 90 to 96 from the UD5 to the UD5-TH since it appeared to me that the only difference was the Thunderbolt port. With his permission, I am quoting his response:
[FONT=Arial, Helvetica, sans-serif][FONT=Arial, Helvetica, sans-serif]Quality also encompasses some other characteristics including the chips used and their implementation.
For instance the UD5 has the same Intel USB 3.1/ThunderBolt 3.0 controller as the UD5 TH, the UD5 TH has two extra PCI-E lanes attached and two much higher quality USB 3.1 Power Delivery 2.0 chips. So the implementation benefits UD5 TH points on the features scale, but the upgraded type-C support chips increase the quality scale. The two chips allow for 12v/3A and 5v/3A output to devices with the new spec, while the normal UD5 (and majority of other boards regardless of their controller) are limited to 5v/3A output.
The UD5 TH also has passed Intel's Thunderbolt 3.0 certification which adds to quality since Intel officially certified the port (and Intel's certification in this regard is actually not easy to obtain), and the PCB of the UD5 TH is different than that of the UD5 in terms of layers (6 vs 4) to increase quality of TB 3 signals so that they can pass certification.
Other than that, the quality of SATA connections is also better, as the UD5 has four SATA ports sharing bandwidth with two M.2 slots, the UD5 TH only has 1 SATA port which might share bandwidth with the M.2 slot for SATA based drives, only if a SATA M.2 drive is installed. While the switches add more function, they also can slightly reduce the quality of the connection, so the UD5 TH doesn't have these and so the quality grade goes up since more SATA is directly from Intel. The UD5 TH also supports HDMI 2.0 through a new HDMI 2.0 chip that the UD5 doesn't have, but that doesn't add to the quality score much.
The differences between the two boards is hard to spot, it's all on and in the PCB, that is why I like to dig a bit deeper.
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[FONT=Arial, Helvetica, sans-serif][FONT=Arial, Helvetica, sans-serif][FONT=Arial, Helvetica, sans-serif][FONT=Arial, Helvetica, sans-serif]Steven Bassiri
CPU, Motherboard, and Overclocking Editor
Tweak Town Pty Ltd
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