Jamie Balfour

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Replaceable SoCs

We all know how infuriating it can be when a computerjust stops working, and repairability is the key to making the world more sustainable. But SoCs in general have made some parts of this easier than before but have also brought many other issues with them.

First of all, SoCs or System-On-Chips are replacements for the architecture that existed for generations where the CPU, GPU, northbridges and south bridges and the main memory are in completely separate parts of the system.

Back in the days of the Core 2 Duo and Phenom and Athlon days we had IGPs (Integrated Graphics Processors) that communicated through the northbridge which meant it was a long way a way from the central processing unit and were therefore slowed by long path that they had to take to perform operations. We also had two bridges; the northbridge (or memory hub) which communicated with the main memory (RAM and ROM) directly from the CPU, and in the case of an IGP, the graphics processor. This was removed first by AMD and then by Intel (you'll actually notice that whilst AMD has always been the underdog in the CPU market, it actually brought some of the best innovations to the market such as x86-64 and HyperTransport).

But we still had the southbridge for a very long time and it continued to provide backwards compatibility with older hardware such as PS/2, RS232 and other obsolete connectors using the SuperIO hub. Lately however, the SuperIO hub doesn't really need to exist and the whole southbridge has been integrated as a chiplet into the main chip (or SoC). Not only does this improve performance, but it reduces power consumption and heat.

The separate chiplet idea is also very feasible compared with integrating everything into the central processing unit or a dedicated external chip as you'll understand if you understand the term binning chips. 

SoCs have problems though

As an advocate for the concept of a SoC architecture over traditional architectures I can see the humongous benefits that they bring, and the bridge the gap that existed before whereby the performance of a computer was affected by how long the wires between different components was, but they do bring one caveat. 

That one caveat is the fact that all SoCs in laptop computers are soldered, often using the BGA-style of socket. This means that the whole board needs replacing when the the SoC has one faulty part, and, with more being integrated into the SoC, this is more likely to happen. This means that not only is it far more expensive to replace a SoC, but it also means that it is far more difficult. 

I've replaced many CPUs in laptops in my teenage years onwards, most notably is replacing my Pentium 4 laptop with a Pentium 4 Mobile-M chip but I would be hard-pressed to try and replace a BGA chip these days. 

How they need to be improved, particularly in laptops

As the Right-To-Repair movement progresses even further, one of the main areas people should be looking to push for is PGA-based or LGA-based sockets that allow direct replacement of the SoC again. Heck, even the Pentium-M CPUs with their Socket 479 sockets were replaceable to the point of remove and slot in. In a world where slimness is the most important thing, we really need to think about sustainability too.

Posted by jamiebalfour04 in Tech talk
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