Wed. Nov 29th, 2023

Key Takeaways

  • Laptop and desktop GPUs often share the same names but have significant performance differences. A laptop RTX 3070 Ti performs closer to a desktop 3060 Ti, for example.
  • To determine the performance of a laptop GPU, look up the architecture, shader cores, ROPs/TMUs, clock speeds, and memory bandwidth and volume.
  • The TDP (Thermal Design Power) of a laptop GPU determines its power usage and performance. Higher TDP allows for better performance, but it may sacrifice slimness and portability. Compare benchmarks to assess overall performance.

You can buy a laptop with an RTX 4090 GPU in it, but is it really a 4090? It has the same name as NVIDIA’s desktop monster, but this and virtually all laptop GPUs are not what their names suggest.

Laptop and Desktop GPUs Share Names and Nothing Else

GPU (graphics processing unit) makers have been confusing customers with their naming choices for years if not decades at this point. With the 30- and 40- series laptop GPUs, NVIDIA is perhaps the biggest offender here, since there is no difference at all in the naming scheme of their laptop GPUs and desktop GPUs. A laptop RTX 3070 Ti for example, is closer to a desktop 3060 Ti in performance, and, while impressive, the RTX 4090 laptop GPU performs like a desktop RTX 3090.

In rare cases, such as with the RTX 4060, the laptop and desktop graphics cards are, in fact, the exact same chip. But in the vast majority of cases the two GPU share nothing except for their names. When it comes to AMD, its naming scheme still goes to the trouble of adding an “M” to the end of its mobile GPU name. Still, that won’t help you understand the real difference between, for example, a Radeon 6800M and 6800. So if you really want to suss out what sort of performance you can expect from your prospective laptop purchase, here are a few things you can do.

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Look Up the Architecture

The “architecture” of a GPU is essentially its technological generation. All GPUs running on the same architecture share features, efficiencies, and relative performance. With current laptop GPUs, the architecture of these mobile chips is the same as that of their desktop counterparts, but this wasn’t always the case and it’s possible that it may one day again be that architectural differences exist between desktop and laptop GPUs.

Either way, you can easily look up the GPU architecture of any GPU using Google. Sites such as TechPowerUp maintain a database of GPU specifications, and so you can double-check that the laptop GPU you’re considering uses the same architecture as its desktop namesake. You can also use utilities like GPU-Z if you already have the laptop in your possession.

Examine the Specs

The next thing to do is look up the specifications of the GPUs in question and compare them. There are a few key specs to look out for:

  • Shader cores: These are the programmable processor cores that do the main work of a GPU. If two GPUs are the same architecture and run at the same speed, then more cores means more performance.
  • ROPs/TMUs: Render Output Pipelines and Texture Mapping Units represent the configuration of the GPU in question. These specialized modules on the GPU don’t tell you anything about performance by themselves, but you can compare the ROP/TMU numbers of a laptop and desktop graphics cards to determine if they are the same chip or not.
  • Clock Speeds: GPUs have a base and boost clock speed. Even when two GPUs are physically identical, they may be set from the factory to run at different clock speeds. As you might expect, faster is better when two GPUs are the same otherwise.
  • Memory Bandwidth and Volume: VRAM is a crucial specification for a GPU, and you can compare the amount, type, and speed of VRAM you get with a laptop or desktop GPU using the same name. Looking up the total bandwidth is useful, since this gives you a clear idea of how a GPU’s memory performs.

Looking up these key specs can give you a good idea of what desktop GPU your laptop GPU is most like. For example, the RTX 4060 has an identical GPU for both laptop and desktop variants, but the desktop model has better, faster memory, leading to a small bump in memory bandwidth.

Comparing the desktop RTX 4080 to the laptop RTX 4090 shows that they have identical shader unit, ROP, and TMU counts. In other words, the laptop 4090 is a desktop 4080, but running with less total power and clock speed. Speaker of total power, that brings us to the next most important issue.

Determine the TDP

TDP or Thermal Design Power is how much power a given GPU is designed to use and then dissipate through cooling. All things being equal, the more power a GPU can use, the better it will perform. Laptops are thermally constrained, so the same GPU in different laptops will have different power limits. An RTX 4060 with a 45W TDP will perform much worse than the same GPU with a 100W TDP.

This is another area where laptop makers can confuse customers. With varying TDP ranges, lower-tier GPUs can outperform higher-tier GPUs with better power limits, or two laptops with the same GPU can perform very differently. This is why you need to look up the TDP for your specific laptop GPU as it’s implemented in a specific laptop. In general you want a laptop GPU that’s at or close to the maximum TDP for that chip, unless you value slimness and portability over performance.

While it may take some digging, manufacturer’s do list the TDP figures for their GPUs, or alternatively you can search for independent reviews of the laptop which will usually list the TDP of the chip.

Compare Benchmarks

Laptops are complete systems, and so focusing just on the GPU in isolation is of limited usefulness. Whether you want a fast GPU for gaming, work, or both, the best way to judge a GPU is through actual performance measurement. This means you need to look up benchmarks for the laptops you’re interested in buying to see how they perform in the games and applications you want to use. This will let you know how that specific laptop performs with that particular combination of components and cooling performance. Because no matter what specifications a GPU (or entire computer) has on paper, it means nothing in the face of actual real-world performance.

Now, hopefully, you’ll be spared from buying a shiny new gaming laptop with very inaccurate ideas of how well it will perform based on the arbitrary names the GPU makers have decided to use.

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By John P.

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