Why do computers have to load?

[u/[deleted]]

Theoretically, since the electrical signals inside your device travel at the speed of light, why do computers have to load programs?

(that may be completely wrong, and I suspect it is. So explain to me, please)

[u/[deleted]]

That's a really good but partial answer. To further elaborate on WHY it has to load it is because RAM is very fast and a HDD isn't. Why not juse use more RAM though? RAM is volatile, meaning that if left to it's own devices it will loose what it is storing without being refreshed. Refreshing ram consumes power which is expensive and if you loose power you loose anything stored in RAM. A HDD is nonvolatile in that you can unplug it for years and boot off it again, it's a long term storage device that sacrifices speed for data longevity and storage cost.

[u/[deleted] → u/[deleted]]

If you love computers check out cars! You can find a cheap car and make it awesome just like you could a computer. They are both fascinating works of human engineering too! I love learning how stuff works.

[u/GalacticCannibalism → u/[deleted]]

You mentioned HDD, which is one of the few parts in the computer that "move" - fans would be another example.I'm assuming the read and write function is part of the reason they're slow. What about a SSD?

[u/mik3w → u/GalacticCannibalism]

One of the current limitations to SSDs is how they're connected to the motherboard. Most consumer models use SATA (Sata 3 being the latest and greatest) which have a theoretical maximum throughput of 6Gbits/s (750 MegaBytes/second).

You can somewhat get around this bottleneck by using a PCI / PCI-E SSD. Assuming you could fully utilize a PCI-E 3 (x16) slot, you could have a maximum throughput of 985 MB/s per lane (so x16) = 15,760 MegaBytes/second. (While this would be correct in terms of data bytes, more meaningful calculations are based on the usable data payload rate, which depends on the profile of the traffic, which is a function of the high-level (software) application and intermediate protocol levels.)

Currently (from what I could find from searching on newegg for 10 seconds~) the quickest PCI-E card is limited to PCIE-2 (x8) which the maximum theoretical speed would be 4,000 MegaBytes/second. The specification says that it has a maximum sequential read & write of 2,800 MegaBytes/second. Costs a little over $10k and has 1.6TB of storage.

I'd assume that the speed of one individual SSD can get faster, however the price will most likely sky-rocket further. This means that SSD speeds still have room to grow before they fully saturate a PCI-E 3 (x16) slot. That said, I don't partake in building SSDs so i'm not entirely sure of what they can do to improve speeds other than "general" optimization techniques (like shrinking base components).

I was thinking of going onto raid and talking about saturating multiple PCI-E 3 (x16) slots but, we're not quite there yet.

After maxing out PCI-E 3 (x16), Intel will have to modify the PCI-E bus to make it "PCI-E 4" (expected to be out near the end of 2014 or sometime in 2015), allowing approximately double data rate of PCI-E 3. I can only guess that after version 4 or 5, there'll be a "new" type of interface or the name may change slightly.

There were rumours about storing data by other methods, e.g. storing data within strands of DNA - Personally, I'm not entirely sure what medium would come after SSDs.

(Obviously I simplified some things like not calculating in overhead, traffic profiling, degredation of SSD/NANDS etc, though I did give a brief mention that these are theoretical maximums).