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February 10th, 2021 03:00
Thunderbolt Docks with Precision 7550 causes throttling
Hi, there is an issue when connecting a USB/Thunderbolt 'dock' to Thunderbolt port which causes the precision to throttle down to 800Mhz.
The throttling seems to occur when....
- After the unit has botted plug this into the Precision 7550, and all good. But the whole unit will throttle down to 800Mhz as soon as I connect my phone to one of the USB C ports of the dock.
- Boot the unit whilst plugged in.
I am using an HP Thunderbolt G2, but I found a YouTube video with someone using a Dell dock with the same issue.
https://youtu.be/RHw2-AKSkSk?t=169
This is a real, reproducible issue with different devices. Can someone in the driver/BIOS division look at this, OR if it's a thunderbolt microcode issue pass the problem over to Intel for resolution? Doesn't look to be too difficult an issue.
jphughan
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February 17th, 2021 08:00
@JimiScott Watched your YouTube video. The guy in the video was using a WD19 180W, which provides up to 130W to the attached system, not the WD19DC that provides up to 210W and is specifically meant to support Precision 7000 Series systems. So it's not too surprising that he had throttling problems. The WD19DC that I mentioned was introduced at the same time as the regular WD19 he's using -- and even if that weren't the case, there was already the TB18DC available that properly powered Precision 7000 Series systems. He also griped in the comments about the low video bandwidth making the triple display outputs "utterly useless". Well, the WD19DC is also able to tap into a lot more video bandwidth than the regular WD19 thanks to its use of a dual cable connection, which is also how it supplies so much power. But even the WD19 can support triple displays up to 1080p each when paired with a DisplayPort HBR3-based system, which I would argue is not "utterly useless".
So that guy ranted about negative results encountered when using a setup that was never designed to support his use case.
DELL-Cares
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February 10th, 2021 09:00
Thank you! We have received the required details. We will work towards a resolution. In the meantime, you may also receive assistance or suggestions from the community members.
JimiScott
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February 17th, 2021 06:00
I spoke to the Dell technician, and after much back and forth....he basically just told me it was the docks problem. It seems the ticket was closed (or I couldn't add additional messages to the thread)....so here's my response.
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What you're saying is that if the dock isn't plugged in there's no problem, and when it's plugged in (under the specific described circumstances) the system throttles...but because it's plugged in, it's the docks problem and not the system.
This is Dell's top of the line laptop. The power management is horrendous. I reported the problem, but you're not prepared to even look at it, just prefer to waste my time.
Thanks...close the ticket, extremely unhelpful.
jphughan
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February 17th, 2021 08:00
@JimiScott Are you keeping the system's own power adapter directly attached while you're docked to that HP dock? The Precision 7000 Series systems are designed for more power than the 100W max of the USB PD spec. Dell did something proprietary on some of their single connector docks to stretch that to 130W, but even that isn't enough in your case, and you won't find that supported on an HP dock. So if your system is throttling it's probably because it's relying on the dock as a power source, in which case you're expecting it to use less power than it's designed to have available, and it's responding by reducing performance to operate within that reduced power budget rather than maintaining performance by continuing to drain its battery while connected to that undersized power source because that will of course eventually cause your system to die. If your system throttles more severely when your phone is connected to the dock, then the dock might reduce its passthrough power output to the system when that happens, which would be a lame dock design.
Anyhow, Dell has a dock called the WD19DC that is specifically meant to support the power requirements of Precision 7000 Series systems by connecting to two USB-C ports on the system, which allows it to supply up to 210W of power. I'd suggest using that dock, but if that isn't an option, keep your system's power adapter connected. That was Dell's own guidance to Precision 7000 Series system owners before they introduced the WD19DC (and its predecessor the TB18DC) to cover this need.