Support more power efficient CPUs for better battery life (AMD 7840U, ...)

Some users (like myself) prefer battery life over maximum performance. Judging from the threads touching this topic, there are quite many users which value battery life higher over the maximum of performance.

I would love to see more power efficient CPUs offered for FW 16. For example the AMD 7840U, etc. I don’t need the raw performance of the top high end CPUs for my work, but rather a maximum battery life for maximum mobility. Anyway I ordered FW 16 with the 7840HS CPU, but I would very much prefer a “U” CPU.

Framework, please support “U” CPUs for FW 16! This could of course also be offered later as a MB replacement option, if it can’t be done quickly.


As far as I understand the situation, the difference is mainly the TDP. U are limited to 25W while HS are allowed to boost up to 35W. If you want longer battery life, you can just limit the TDP via software on your 7840HS to match that of a 7840U.


While you are right that you can limit the max power of the 7840HS that way, I am not sure if
that will be the same as having a 7840U.
Let me say it this way: when you have a fuel-guzzling big car engine, and a cost-effective small one, you can limit the big engine to not use more max energy than the small one, but the big engine will still burn more fuel, because it will still burn more when it is not at max throttle. Most of the time, you don’t drive at max power, but below - and the large engine will burn more at that.
So unless the 7840HS and the 7840U are the exact same CPU (incl. software), and only differ in max TDP, I don’t think that will solve the issue.

But I am not a CPU expert - maybe someone who is could shed some light on this?

Technically all the AMD CPUs that Framework offers are physically the same CPU design and made by the same machines.

However minor differences do tend to occur in the manufacturing process. Some have slightly better performance at low power consumption (those get labeled 7840u), some have slightly better performance at high power (those get labeled 7840hs), some have even better high power performance (those get labeled 7940hs), some have a dead core or two (those get labeled 7640u or 7640hs).

So the 7840u and 7840hs are physically the same CPU design and made by the same machines. However due to minor differences that occured in manufacturing the 7840u should have slightly better performance at low power while the 7840hs should scale better to higher power.

Notice the word “slightly”. Years ago the variation between CPUs was pretty substantial, however as manufacturing processes have improved the differences have generally become a lot more minor.

So a 7840u would likely have slightly better performance than a 7840hs if the 7840hs was limited to the power consumption of a 7840u, however I doubt it would be a meaningful enough difference to justify a 7840u variant of the mainboard.


I’m generally with you on this. I think it usually makes more sense for a laptop to prioritize battery life over CPU power since that power is superfluous for most users, but everyone can benefit from longer battery life.

But if that’s the case, if I were buying for best battery life, I’d get a Framework 13 with the smallest CPU. I think the power savings from a smaller screen and fewer features far outweighs the power savings of a less potent processor, especially since most of the time the CPU is not running at TDP, and an idling U-class isn’t saving you much energy over an idling HS-class.

I think it’s a bit like trying to get a high-MPG SUV. By the time you’ve nerfed it enough to compete with a car, you might as well have just bought a car instead. I deliberately chose power over battery life when I chose a FW16, so I’m glad it’s HS and not U.

This is something that I’m also very interested in. My ideal laptop would be a framework 16 with an expanded battery in the expansion bay and a power sipping ryzen u-series CPU. I’ve spent a bunch of time shopping around for another laptop with a Ryzen U-series cpu paired with a high capacity battery (85+Whr) but have found none. All laptops I’ve found with the U-series chip seem to use a battery of around 47-67Whr. If these deviced shipped with an actually large battery, like 95-99Whr, they could destroy the competitions battery life. But alas I guess I’m part a of niche consumer.

Looking forward to getting hands on with my FW-16, if no one else does I’d like to build an 18650 based battery expansion module that enables hot-swap. If USB-C power delivery can be utilized over the pcie connection, then in theory the battery could be swapped out while the device is still running and be as large as one’s willing to carry. Not to mention 18650’s making the battery cheaply and easily repairable (at the cost of size and weight).

Ok, thanks for pointing this out. So the difference from the 7840U and a throttled 7840HS should be minor.
But to be complete, let’s not forget there are other advantages with the 7840U:

  • it is less expensive. if you don’t need the performance, you can save money
  • with the 7840U, you don’t have to care about setting up and maintaining the throttling - as it already works the way you want.

This in addition to the efficiency advantage is (IMO at least) enough reason to offer a “U” CPU.

Let me say on top of this, the “7840U” is a random pick. I am sure I would also be fine with an even slower CPU. I know this may sound surprising for some, but that’s a fact. When I need to run workloads that require high performance compute power, I use the cloud / external infrastructure. A laptop is not a viable choice here, even with fastest mobile CPU available. I believe IT engineers will increasingly work like this in future. And then there’s just users with not-so-good or bad eyesight, who need to be somewhat mobile, but don’t require much CPU power. Etc., etc., many more examples. I believe the times are over where you always really needed the fastest CPU on you laptop, like 15 years ago. This has changed.

This is definitely reasonable, but only works for some people. The workloads people run are just more diverse than “power user → big power hungry iron”, *office user → weak power efficent laptop".

I have a mandatory requirement for a much larger screen than 13". But a U CPU would be fast enough for me. Another requirement for me is good battery life. That’s why I am actually better off with a slower CPU. I am sure there are many users which don’t require the fastest CPU, but a large screen. FW 16 is supposed to be a very flexible high-end laptop, so there should be many possible configurations for all kinds of workloads.

They are indeed the exact same CPU. Just with minor tuning differences.

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Yeah, and I think that kinda puts you in this tough spot. It’s my understanding that the display is really the biggest power draw on a laptop since it’s pretty much a continuous draw whereas the CPU can drop down to just a few watts for a large amount of the uptime, rarely drawing as much as the display does. That said, I can’t actually say for sure there is much power saved by choosing a 13.5" over a 16" panel. I can’t find good numbers anywhere so it too may be negligible, especially if you use your brightness wisely!

There are still all the additional components that the 16 has that are all opportunities for parasitic drains even if you don’t use them, so I’m still skeptical if a U-series CPU would really give you much. I’m just guessing about all this, though, and you’re totally right that it does fit the spirit of the design to have as many options as they can sell. If only laptops could return to socketed CPU’s!

Man, imagine a FW with a socketed CPU… This is the dream.

Is it?

Afaik the price of the 7840u and 7840hs is not public information, however afaik generally laptop CPUs that are pretty similar other than power class are similar in price.

Intel does list recommended prices for their laptop CPUs, but those are wildly inconsistent (ex. The i7 1370P is listed as $42 cheaper than the lower tier i7 1360P, if that was actually the case then I doubt Framework would offer the 1360P in the Framework 13) and not useful.

IIRC several years ago some laptop brand (I think it was Asus) indicated they paid similar amounts for the Ryzen 7 3750h and Ryzen 7 3700u, which are related in the same way that the 7840hs and 7840u are related, so I’d expect the 7840hs and 7840u to cost similar amounts.

Yeah it’s true that a 16" isn’t ideal for battery life, but you have some hard requirements, this is one for me.

I may have picked a not-so-good example with the 7840U, because it is too close to the 7840HS. I am sure I could work well with an even slower and more efficient CPU than the 7840U. I just don’t care for and don’t need big and red-hot CPUs.

Hopefully there is some difference, but yeah I think if you don’t really need big power, why not drop all the way down to a Ryzen 3? For most of the things we do on a daily basis, I’m sure it’s still more than enough! I think that’s enough differentiation to make sense for Framework to build an entire new mainboard, especially at this stage in their growth.

What you are doing is also going to be a large factor in your battery life. You can have something like a 25 watt and 45 watt cpu and have pretty much the same battery life if you are just browsing the web, typing up notes, and generally using it lightly. With light use both are going to be sipping just a few watts and not consuming max tdp. With light use I see something like switching the screen from 165Hz to 60Hz or something giving a bigger battery boost than a lower tdp CPU.

Yeah, very likely an R3 or R5 would do.
Remember the times where everyone absolutely had to have the fastest possible CPU in your laptop, because they were actually required to do any meaningful work. I had the fastest possible CPU back then too. A couple years ago, I have reached the point where I did not require the fastest stuff anymore, at this point you don’t want to have them. Some people still require the fastest stuff, but I believe the number of people keeps increasing over the years who don’t, as laptops get ever-more powerful, and many people don’t do gaming etc.

I believe this is a viable reason for a company like Framework to offer an option. Just like with memory, where you can pick 8 GB if that works for you, or 96 GB, if you need that. It should be exactly the same with CPU I believe.

It’s not as simple as you are presenting it to be.


Socketed CPUs are detrimental to battery life and will negate any, if any, gains from a U series processor. The high power draw of socketed CPUs is one of the many reasons it is no longer offered in most laptops.


How does the mounting mechanism affect battery life?

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  1. Signals between the CPU and motherboard tend to degrade when going through a socket. So to ensure that the signals still work properly the power is cranked up.

  2. Most soldered CPUs (especially on AMD) are typically optimized for lower power (as they are expected to be used in laptops).

To elaborate on that last point, most of AMD’s socketed/desktop CPUs are actually split into multiple smaller chips known as chiplets. Dividing a CPU into multiple smaller chips makes it cheaper/easier for the manufacturer to scale up performance, however it introduces the need for power-intensive communication between chips, which is why AMD doesn’t do that on most soldered/laptop CPUs.

Further AMD often uses a newer and more efficient manufacturing process (ex. TSMC 4nm currently) on their soldered/laptop chips but an older and cheaper manufacturing process (ex. TSMC 5nm and 6nm currently) on their socketed/desktop CPUs.

There are some exceptions to that, such as the AMD 7045 series CPUs (ex. 7945hx3d) which are just soldered/laptop variants of normal AMD socketed/desktop CPUs. AMD also often releases socketed/desktop variants (most models ending with a “G”) of previous generation soldered/laptop CPUs, although that is previous gen at launch so not many people want those.