RAM-capacity matters.<p>Apple products have chosen to have higher-speed RAM that has lower capacity. PC users have the more standard (higher-capacity, but slower) RAM modules.<p>I'm sure everyone remembers the crazy MiniZinc benchmarks on Apple products, as well as other incredible RAM benchmarks. Yeah, when you directly solder RAM to the motherboard, and/or directly stack the RAM on top of the CPU, you can make more assumptions about communication... and that channel can likely have lower capacitances or other physical features.<p>Even 10-centimeters is about 2-clock ticks (assuming 4GHz clock), aka 0.5 nanoseconds, worth of distance. So that physical distance is in fact a substantial distance away when we're talking about nanosecond-scale communications that regularly take place between a CPU and RAM.<p>---------------<p>But its a tradeoff. By having the assumption that RAM is further away in typical PCs, we can stuff more RAM 10-centimeters away or 20-cm away on larger server motherboards (aka: sticks-and-sticks of different RAM).<p>But Apple makes a much smaller assumption: 0-cm... directly soldered on top of these M1 chips. Guess what? After 8GB of RAM, they've run out of room and they literally can't expand anymore unless they increase the assumed centimeters worth of distance out.<p>BTW: Thank your EE for equalizing all the trace-lengths to all your RAM chips. Don't believe me? Take a good look at a motherboard close to the RAM and/or CPU, I guarantee you'll see the "wavy" lines of PCB-traces as the EE in charge of the PCB-design is trying to trace-length match all the different wires to the RAM.