Why laptops suck for simulations

[Mathijs Kok 30862]

Check out my PC. It’s a silly one, I agree, I build it for fun and because I sit behind it 12 hours a day and love to see how things work. But check out the fans. There are two for the GPU, three for the CPU (total overkill but I overclock like a lunatic), one in the PSU and two small ones that cool bits of the mother board. These are needed because contrary to what many people think a completely open case is very bad for cooling as you have no air flow.  So that’s 8 fans that are cooling my machine. As said a silly machine but in almost every PC intended for gaming you will find at least 5 rather large fans.

 

Now check out your laptop. No way 5 of those big fans will fit in there.  Most of the time there is only one 5 cm fan in a laptop.  And that, dear friends, is the reason why laptops and simulations (or any major game) do not work well together. The issue is called Thermal Throttling. Thermal Throttling happens when any part of the computer overheats (most often the GPU or CPU) and slows down to prevent overheating and melting.

 

I think we all know a modern computer running at full blast generates a lot of heat, but I think many people underestimate exactly how much. Mine can use up to 480 watt and 98% of that is somehow converted into heat (the rest radiates out as radiation that is not easily converted into heat).  Put four of these in an office and you do not need a heater in winter. More problematic, the heat is generated extremely locally, in a system like mine the total surface of the CPU and core GPU chips is perhaps 3 square centimeters and most heat is generated in that area.  That’s why cooling PC’s seems to be a complete hobby for many people.

Now look back at your laptop. See the issue? There is no way you can run desktop components in a laptop because they create too much heat. So special laptop CPUs and GPUs are used that run on lower voltages and lower speeds, those create less heat and avoid most of the problem.  And most of the time that works great. Using most software, surfing the net, watching video etc your CPU and GPU are idling away at 3% with sometimes a burst of more use. Perhaps even to 100% when you unpack a file or something. No problem, nothing will overheat in those conditions. Things change dramatically when you ask the GPU and CPU to run at high loads for a longer time. If the cooling is not adequate things will overheat and to save you from seeing a very expensive small puff of smoke they will throttle down to a level that can be maintained indefinitely. 

 

And THAT level is what determines how fast your laptop is for serious simulation. How fast the machine can run at near 100% load is the speed of the simulation.

 

The actual level depends a lot on the hardware. Some laptops have better cooling, many have serious limited cooling.  Some have high end components some lesser. To make thing worse, almost never does a manufacturer tell you that speed. Take for example one I got here on my desk. It has a i7-7700HQ CPU running at 2,80 GHz and a 1050 Ti graphics system, 16 Gb of DDR4 memory.  That should be fine for any simulation, right? Well actually not, after starting P3d V4.1 on it things feel great, good fps…. Uhhh wait a second, did my framerate just drop a lot? And did it drop even more a few seconds later?

 

Yes it did because the GPU reached 92 degrees and throttled down to 700 MHz from the standard 1400 MHz and seconds later the CPU reached 80 degrees and throttled down from 2800 MHz to 1600 MHz. The temperatures then dropped to acceptable levels but the MHz’s did not go back to normal until I closed the sim. So basically, this is a 1,6 GHz laptop with slow graphics card when you push it. Keep in mind this is not something dishonest from the people making the laptop. Having 2.8 GHz available is very useful, but having it available all the time would be better. But physics are what they are, in a thin laptop you simply do not have the space to handle the amounts of heat that are generated. 

 

 

If you want to be able to run high loads indefinitely you will need a specialized laptop. A laptop designed for serious gaming. Those are never thin, never light, never have good battery life and are never cheap.

 

Detecting thermal throttling can be hard. I seen many laptops that throttled down even when the sims was still loading (if that takes 2 minutes). So you would NEVER see the sim running at the frames the CPU might be able to run if it was cool.  But there are many tools that show the the temperature of the CPU and the speed that can help. HWiNFO for example is very good and easy to use.

 

So, what can you do? Not a lot unfortunately. There are few things that help a bit though.

 

• If the bottom of your laptop gets hot, make sure it can get rid of that heat by allowing air to flow underneath. Get a laptop cooler, even though I find these things almost always a bit silly.
• Consider X-Plane (if you are a flight simmer). It only uses two cores and seems to be a bit more gentle on graphics cards without downscaling the graphics.
• Consider moving the GPU out of the machine. They are called eGPUs and there are a few available. I tried the Alienware Graphics Amplifier and was pleasantly surprised. Razer has the Core V2, Asus has one and a new one called the Breakaway Puck seems to be pretty cool as well.  Do check the connections though because many require Thunderbolt 3.
• Keep things clean. If you ever checked the fans in any bit of electronics after a few years of use you will undoubtedly know how they get caked with dust, hairs and other debris. Inside your laptop with it’s very small fans and heat dispersing surfaces this is a big issue. Certainly, if you ever use your laptop on a couch, bed or anything else then a pristine table. It’s like a small portable hoover, sucking up dirt. If you do not keep the air cooling circuits clean you lose a lot of your cooling very fast.  Laptops that make it hard to clean should be forbidden.

 

Basically, the answer to the question, ‘can I use a laptop to run my complex simulator’ is simply no. Unless you spend a lot of money and get one that is designed to run hot.

 

[Mathijs Kok 30862]

A Dutch article on this that has very good data: https://tweakers.net/reviews/5909/throttling-van-laptops-vandaar-die-variatie-in-prestatie.html