X1 Yoga 3rd Gen Decreased SSD performance with Thunderbolt 3 Dock (1/3 of AC Power w/ "Coil Whine")

Question

(Originally posted on Lenovo Forum)

Hey group,

While testing the performance of the SSD in my X1 Yoga 3rd Gen (X1Y3) with CrystalDiskMark, I noticed a drastic performance drop in 4KiB Q(ueue)8T(hread)8 when connected to the Thunderbolt 3 Dock as compared to connected to AC power:

Dock:

Random Read 4KiB (Q= 8,T= 8) : 318.764 MB/s [ 77823.2 IOPS]
Random Write 4KiB (Q= 8,T= 8) : 256.349 MB/s [ 62585.2 IOPS]

AC Power:

Random Read 4KiB (Q= 8,T= 8) : 943.671 MB/s [ 230388.4 IOPS]
Random Write 4KiB (Q= 8,T= 8) : 1024.264 MB/s [ 250064.5 IOPS]

I noticed that with the Dock, the CPU usage during the test was only about 50%, whereas on AC power it was about 100%.

With the performance drop, I also heard very audible "coil whine". I can't quite tell if it was only coming from the dock or both the dock and the laptop. All connected devices were unplugged from the dock. The only two cables connected to the dock were the AC cord and the Thunderbolt 3 cable. The noise is NOT heard while using AC power. I thought the noise was just annoying before, but now with this performance drop, I'm a bit more concerned... Based on my experience with Lenovo Tech Support, I don't think I'd get any real advice from them. I was wondering if anyone else noticed the same issue and what do you think is causing it? Thank so much for your help!

This X1Y3 is a replacement of an X1 Yoga 2nd Gen (X1Y2). The X1Y2 didn't have this probelm at all (neither "coil whine" nor performance drop). The other three tests, Seq Q32T1, 4KiB Q32T1, 4KiB Q1T1, did NOT have issues either. UPDATE: No coil whine noticed during pure CPU test with IntelBurnTest. CPU was used at 100% as opposed to the 4 KiB Q8T8 test 50% CPU usage on TB3 Dock (but 100% on AC). It makes me wonder if it's SSD related. (thank you, https://www.reddit.com/user/navindian, for the suggestion!)

X1Y3 Machine Model: 20LD001FUS
X1Y3 Thunderbolt Software Version: 17.3.72.250, controller driver version: 17.3.72.2.
X1Y3 Thunderbolt Firmware Info: NVM 33.00, PD firmware version displayed, but based on driver info on Lenovo website, it should be F : 407.06.12
X1Y2 Machine Model: 20JDCTO1WW
X1Y2 Thunderbolt Software Version: 16.2.55.275, controller driver version: 16.2.55.1
X1Y2 Thunderbolt Firmware Info: NVM 15.00, PD firmware version f201.13.00