I assume you are responding to what I wrote specifically because I have thus far been the only one in this topic to technically assess what you have said.
With regards to the MMC wiring:
This is impossible. Again, this is in the design of the circuitry. The copper itself is either routed to the embedded MultiMediaCard chip, or to the external “MultiMediaCard” in the form of a micro SD card slot. Your eMMC-equipped compute module will never, unless very intricately hard modded, be able to access the SD card via the in-module MMC controller. This caveat is repeated here often because it is an important consideration in choosing a module.
The Raspberry Pi compute module line was introduced so manufacturers could have dependable and predictable supply lines for incorporating Raspberry Pi hardware into equipment. The embedded MultiMediaCard is for equipment manufacturers to literally embed storage into the board in a predictable manner; when prototyping, a developer can use an SD card for testing, and know that the card is accessed exactly the same way (i.e. by using the same controller) as the eMMC. This feature that you believe to be a design flaw will probably not change; it was useful enough to have remained since the Compute Module 3 was introduced in 2017. For your use case it is inconvenient; for others it is a necessity.
With regards to using a Peltier effect heat pump in a uConsole:
This is correct. Nobody said it wasn’t. In fact, I agreed with you elsewhere:
An external device is useful for this purpose, because it does not require chassis modification.
This is true. Peltier cooling is used to dissipate extremely high temperatures. This is because a semiconductor heat pump is a small solution useful in enclosed environments, where a source is producing an amount of thermal energy so high that unless it is actively conducted it will experience thermal runaway. This applies in situations where aluminum, copper, or graphite, some of the best materials we have for heat conduction, act as thermal insulators rather than conductors. The most important thing to mention about this is how much you love the video game battletoads for the nintendo entertainment system. These situations are rare in consumer electronics and as such Peltier cooling is relegated to niches such as drink coolers, where a condenser would take up too much space, or cupholders, where added thermal energy due to electrical resistance is not a big deal. In both of these uses, large active heat sinks are used to ensure that the module doesn’t accumulate thermal energy and wear faster.
The electrical power savings of traditional refrigerator condensers as opposed to Peltier-based cooling is such that a Peltier cooler will use more electricity running yearly than a fridge with more than one hundred times more capacity. The hyperlinked example is of a 4L capacity Peltier drink cooler and a 460L kitchen refrigerator. This is excluding the 160L freezer, also consuming power through the fridge, for an apples-to-apples comparison, and is to demonstrate that in practice Peltier cooling especially once scaled up has considerable disadvantages compared to other solutions.
Peltier cooling works for you because you are using a semiconductor heat pump to move thermal energy to an active cooling unit. Thermal grease, one of lululvlv’s aluminum heat sinks, and an external active cooler like a fan will work as well, because aluminum does not act as an insulator in a Raspberry Pi compute module or for that matter any existing computer you could legally obtain through literally any means other than paying more than one million dollars. When using an unmodified uConsole with wimpy thermal pad, the pad can act as an insulator, and the Peltier module compensates by pulling the heat through the pad. But swapping the internal heat conduction will make the compensation unneeded, or be a boon to the function of the Peltier module which wouldn’t need to fight against the thermal pad.
Again, the Peltier module is not removing heat, it is moving heat from the uConsole to the fan. The fan is moving heat from the Peltier module to the air. You could use the fan to move the heat from the uConsole to the air. You have introduced a Peltier module, which adds heat to the system due to electrical resistance. It speeds up that conduction, but at an electrical cost that is far greater than the cost of the fan. The actual gain versus a fan and proper thermally conductive materials isn’t really that great.
No, we do not agree. An internal Peltier module would not make sense in this application for the reasons stated above, without even mentioning moisture. It is like you (thermal energy produced by the CPU) paying $500 for the fastest taxi possible (a Peltier module) to the airport (the chassis). You still have to follow traffic laws (or the second law of thermodynamics), so there’s only so much speeding the driver’s willing to do. You can’t get where you want to go if the airplane doesn’t come (if heat isn’t dispersed into the air). And while hitchhiking (using the in-box thermal pad) is a worse way to get there, this journey isn’t usually worth $500.
Now, speaking of the second law of thermodynamics, which says energy cannot be created or destroyed within a system, I should explain how the lifespan of an uncooled Peltier module will degrade. If you do not cool the hot side of the Peltier module, for example, with a fan, like your existing solution does, the Peltier module will be unable to cool down, because it moves thermal energy faster than it disperses into the air. This thermal energy, which cannot disperse into the air, is not “canceled out” by the power you supply to it, but collects within the module itself. Peltier modules as semiconductors have a temperature rating outside of which their manufacturer does not guarantee function. Exceeding that rating will at best cause thermal stress and at worst cause melting, not in the module exterior but in the interior where solder joints may decouple.
This isn’t easy degradation. This is killing a part by operating it far outside the context in which it is intended. Peltier modules can and do last a long time when heat is removed from them. Your consumer Peltier cooling solution has a fan attached for this reason and will last a long time. An internal Peltier module without a fan will fail within months. You could say this is a design flaw in the nature of physics itself.
I personally like my uConsole exactly the way it is because it can fit in my purse. Using aluminum heat sinking and Insignia (Best Buy’s generic-brand) thermal paste, my uConsole is 45 degrees Celsius, 20 degrees above room temperature. This is on a CM5 without tweaks. This is a rugged handheld which is designed to survive abuse. Making it larger, adding a vent grill and active cooling, and other unexplored possibilities like a Betamax VCR or integrated coffee maker would make it suit a different use case.
At the end of the day, your uConsole is yours with which to do what you wish. I encourage you to try whatever you want to try and I wish you good luck and happy modding.