Put the CPU on a different PCB than the rest of the Mainboard?

Hey guys!

I was wondering if it would be possible to put the CPU on a different PCB than the rest of the Mainboard? Then you would interconnect the Mainboard and the CPU via some connector that has a high enough bandwidth to do the job (is PCIe enough? I don’t know). Since we can’t have sockets for CPUs in laptops, this would allow one to upgrade the CPU without have to replace the entire Mainboard?

You could imagine doing the same for soldered RAM modules, if you can afford the room to have SO-DIMMs, simply replace the PCB with the RAM modules for bigger ones?

I’m sure there is a technical reason as to why it’s not feasible otherwise it would have been done, but I searched and can’t seem to know how to phrase it properly, so I can’t find the answers

Thanks in advance!

we can in a sensibly sized laptop chassis. my HP probook is socketed. it’s only wannabe macbooks that are too small for socketed cpus.

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Oh, ok I had read that it was because it was too fragile to be in a device that is carried around everyday. How large is “sensibly sized”?

15 inch and not paper thin. the chassis is around an inch deep

Is that some sort of desktop chip? I thought one reason you can’t do a socketed laptop is that Intel won’t sell you a laptop grade CPU in the right package.

Yeah that won’t work. The problem is latency. As interfaces get higher and higher in speed, tolerances on latency get smaller and smaller. Furthermore, PCIe goes up to x16 not the full 20 lanes that the CPU can do so you would need multiple connectors. these connectors are also quite wide and create an additional point of failure. This would also increase power draw. Numerous design challenges would need to be overcome. At the moment, Framework has created the most elegant solution yet to this problem and even then it isn’t flawless. Sure replacing the mainboard when all you want to replace is the CPU kinda sucks, but at least you aren’t replacing the chassis, display, keyboard, etc.

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no, it’s an AMD laptop chip. Socketed Intel chips do exist, but if they’re uncommon that’s an entirely business decision on the part of Intel. There’s no technical reason a laptop chip can’t be socketed.

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Thanks for the explanation, it all makes sense! Is it a general rule that having a connector increases power draw? (because although there is contact, it’s not the same circuit so there’s an energy loss there?)

Yeah I figured Framework had come up with the most ideal solution, even if it was possible (say with an imaginary PCIe x20 and a connector that isn’t absolutely chunky) it would probably be very expensive to manufacture anyway so most likely not worth it if you are trying to make a profit off of laptops.

Pretty much, take SO-DIMMS vs LPDDRx for example. The soldered stuff can take less voltage for a given speed and thus reduce power draw. There are benefits to soldering stuff to the board, don’t let anyone on here tell you different. It’s just a matter of tradeoffs and what the manufacturer and the consumer are looking for in a laptop. Part of the reason why Apple’s laptops have such tremendous battery life right now is that it’s an SOC (System-On-Chip) so pretty much every thing is located right next to one another in close proximity. Less distance requires less power.

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Intel has te tendency to change CPU socekts and chipset quite often. I think AMD is doing it little less. Even you would socket your intel, you d end just replacing it with the same one , if it would break.
Intel s own way is the compute module for several years now = CPU +chipset + RAM.
Framework as been doing different with its design, ading the replacable RAM modules, but integrating usb connexions and cooling.

This reminds me of the good old days of Acorn Risk PC. Where you could insert SEVERAL of this kind of intel compure unit in a single PC (arm based). Not really the launch of an apple product :smiley:

image
It was even more crazy than that, you could have “guest” processor, like an ARM and a x86! Nowadays you d do virtualisation emulation…

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There are really two sensible places to modularize the CPU:

  1. By using a socketed CPU. As folks have noted in this thread, that means a >1" thick laptop using a high wattage CPU designed for desktop use.
  2. By putting the CPU together with the critical voltage regulators on a board with connectors to the key modules. This is what the Framework Laptop Mainboard already is :slightly_smiling_face:
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not necessarily, there ARE socketed laptop cpus. Mostly AMD but intel have done it in the past.

As far as I know there is no socketed AMD Mobile CPUs SKUs, either way it is much harder to swap a CPU rather than a mainboard.

they exist because I’ve swapped the one in my hp probook.

I’d also be interested in the SKU (or Pro Book model) as afaik, all FP5, FP6 and FP7 are all BGA-only packages.

its a probook 6465b, I upgraded it from what it came with to the highest option one.

The socketed Intel mobile CPUs are quite old. I bought a used touchscreen PC for $5 on a whim, because it was $5! It came with an Intel Celeron T1400 (I think) on Socket P.

That socket used a really nice slim retention mechanism, you just turned a screw.

I upgraded it to a Intel Pentium T4400 for something like $30 off eBay.

I still have the old T1400 if anyone wants it. But it’s worth far less than the postage.

This is old stuff from 2008, a Raspberry Pi will run circles around it.

That’s a laptop model that was EOL’d back in 2012, it looks like. Awesome that it’s still working for you/that you’re getting use out of it. It’s indeed socketed, using AMD’s Socket FS1, AMD’s second to last mobile socket (Socket FS1r2 in 2012).

It seems like you’ve been referencing that laptop as to why it should be possible to have a socketed CPU, but really, it illustrates why Framework (or any laptop manufacturer) can’t actually make one. From FP3 on (2014), AMD has simply not made any socketed mobile chips, and I assume Intel is similar. This goes beyond the CPU btw, since a mobile platform also requires power, thermal management, bridges, controllers etc - everything that’s on a motherboard and basically needs to be replaced for each generation anyway. Everything socketed in recent memory has been “desktop replacement” luggables that basically stuff desktop parts into a “mobile” chassis.

Even with the socketed platforms btw, it looked like AMD/Intel were making incompatible platform changes every generation or so anyway, so I’m not sure what you actually get from doing a chip swap.

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Its an apu so a higher model gets a big boost in gpu as well as cpu speed.

It seems the ‘new’ main board, from the images, come with a heatsink and fan and memory.

If I wanted to upgrade the CPU why would I want all those periferals??