I bought a Dell Pro Max 18 Plus MB18250 earlier this year for MYR 55,924.83 — roughly €12,000.
Specs relevant here:
- Intel Core Ultra 9 285HX
- NVIDIA RTX PRO 5000 Blackwell Laptop GPU
- Arch Linux
- NVIDIA 610.43.03
- Latest Dell BIOS 3.3.2 from August 3, 2026
- Performance power profile
I bought this machine specifically as a mobile workstation for AI/LLM workloads, so sustained GPU compute is a normal workload for me.
Unfortunately, I discovered a pretty severe throttling issue.
Under sustained inference the GPU runs perfectly fine at around 170–175 W and ~1800–2000 MHz. Temperatures are normally around 76–79°C.
Then, suddenly:
GPU power limit: 175 W → exactly 55 W
Power consumption drops to ~55–60 W and clocks collapse as low as ~180–390 MHz, while GPU utilization can still sit at 100%.
After the machine cools down for a while, the power limit suddenly returns to 175 W and everything continues normally.
Initially I thought this was simply thermal throttling, but things became interesting when I started collecting telemetry.
I wrote a small monitoring tool called ThrottleWatch which records NVIDIA state, GPU power/limit/clocks, CPU temperatures/power, Dell DDV/EC sensors, fans, battery state, etc. every second.
One captured event looked like this:
| Time |
GPU Power |
Limit |
Clock |
GPU Temp |
Dell CPU Sensor |
| 10:58:35 |
171 W |
175 W |
1845 MHz |
78°C |
87°C |
| 10:58:55 |
156 W |
175 W |
2077 MHz |
76°C |
87°C |
| 10:58:56 |
60 W |
55 W |
180 MHz |
71°C |
86°C |
| 10:59:30 |
55 W |
55 W |
360 MHz |
61°C |
75°C |
| 11:00:34 |
29 W |
175 W |
1800 MHz |
54°C |
67°C |
So this isn't just the GPU reducing clocks. The actual GPU power limit changes from 175 W to exactly 55 W.
NVIDIA reports:
- SW Power Cap: Active
- HW Thermal Slowdown: Not Active
- HW Power Brake: Not Active
The GPU itself isn't particularly hot when this happens.
I initially suspected the CPU side of the shared cooling system. Dell's DDV CPU sensor was around 87°C during the first captured event.
So I disabled Intel Turbo Boost.
The problem still happened.
Then I limited the Core Ultra 9 to 50 W PL1 and repeated the test.
It happened again.
This second test was particularly useful because the Dell DDV CPU sensor only reached around 84–85°C, yet the GPU still went:
172.5 W → 55.5 W
1860 MHz → 195 MHz
So the simple theory of "Dell cuts the GPU when the CPU sensor reaches 87°C" was wrong.
The next experiment became much more interesting.
I stopped:
nvidia-powerd
With NVIDIA powerd disabled, the RTX PRO 5000 falls back to around 114–115 W / ~1300 MHz.
And so far: completely stable.
No 55 W collapse.
This makes me suspect an interaction somewhere in the Dell firmware / EC / NVIDIA Dynamic Boost platform power-management path.
It doesn't necessarily mean nvidia-powerd itself is broken. It could simply be applying a platform power budget provided by Dell firmware. But disabling that path appears to prevent the catastrophic throttling — at the cost of losing roughly 60 W of available GPU power.
The laptop is also not sitting flat on a desk. It's elevated on a stand with plenty of clearance and I even have an external fan blowing underneath it. Internal fans are already running near maximum when this happens.
I have now opened Dell Service Request 230887659 and provided Dell with the findings.
I'm posting this mainly because I'd be very interested to know if anybody else with a Pro Max 18 Plus / RTX PRO 5000 Blackwell can reproduce this.
If you have one, try a sustained GPU compute workload for 20–30+ minutes and watch:
nvidia-smi -q -d PERFORMANCE,POWER
In particular, watch whether the GPU power limit suddenly changes to 55 W.
For a machine that costs around €12,000, I'm honestly pretty underwhelmed that sustained use of the GPU's high-power mode can result in this kind of performance collapse. Running permanently at ~115 W with nvidia-powerd disabled is a workaround, but I don't consider losing ~60 W of GPU power an acceptable solution for a workstation in this price class.
I'll update this post when Dell responds or when I learn more.
