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Thanks For the Memories: Touring the Awesome Random Access of Old (hackaday.com)
szczys writes: The RAM we use today is truly amazing in all respects: performance, reliability, price; all have been optimized to the point you can consider memory a solved problem. Equally fascinating is the meandering path that we've taken over the last half century to get here. Drums, tubes, mercury delay lines, dekatrons, and core memory. They're still as interesting as the day electrons first ran through their circuits. Perhaps most amazing is the cost and complexity, both of which make you wonder how they ever manage to be used in production machines. But here's the clincher: despite being difficult and costly to manufacture, they were all very reliable.
Yes and no, if you are thinking about your computer or single server sitting beside you. If you are thinking of next gen data centers and virtualized servers, being able to supply a bus to RAM over a fiber link is very interesting. Think of a server component or appliance you install into a rack, then fiber link to your Hosts to supply more ram. There is a limit to the amount of ram slots on a server, a physical limit. Fiber links would open up the ability to have external ram that doesn't actually need a slot. Fiberlinks take considerably less space. And if this was an option, I suspect you'd have a fiber trunk coming from the host. This could actually be genius.
Saying that a problem is solved is risky. Remember that the physics was solved shortly before Einstein et all! The future might reshape our perception, with for instance RAM and ROM convergence: https://en.wikipedia.org/wiki/...
Optical interconnection is very efficient and good fidelity and low interference, but ease of manufacturing complex interconnection and creating multiple permanent connections is still lacking, compared to electric/metal. In addition to that, drivers/receivers are bulky and dissipate too much power. Before photonics can replace electronics, there'll have to be a revolution in miniaturisation and low power for fiber drivers/receivers, as well as analogue mass production technological processes to board etching and component soldering of today.
Alpha Particles from space do not penetrate the building that the computer is in, nor the computer case, nor the plastic package of the memory devices themselves.
Alpha particle bit errors are caused by alpha particle emissions within the memory cell itself, as there is a minute amount of radioactive material in all semiconductor devices, including memory.
However, radiation-induced bit errors are seldom actually caused by package alpha particle emissions. The more likely space-related culprit is neutron flux. It has been found that DRAM bit error rates increase dramatically with altitude, and that solar events increase the rates further.
Fun stuff.
The bit flips aren't due to neutrons, but to other high energy particles (cosmic rays).
And modern memory design tolerates this quite well (on chip EDAC, for instance).
But that's not the dominant source of errors any more. It's more things like electrical noise (signal integrity is another term). As you reduce the size of the device holding a single bit, you're starting to get down to where the thermal noise is a significant fraction of the "signal" (i.e. the presence or absence of charge in that bit storage).
On the other hand the relationship between a system's reliability and the reliability of the system's components isn't one-to-one. You can build unreliable systems out of reliable components, and more surprisingly, you can build reliable systems out of unreliable components. That latter principle is the basis for the Internet, which provides end-to-end communication that is more reliable than any of the possible paths between those endpoints.
Every component is unreliable to some degree; as it becomes increasingly reliable it moves from unusable, to something you can work around, to something whose potential failure you can ignore in many applications.
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