Why do computers start up so fast now?


I remember computers used to take sooo long to start up, that you can press the power button and go make yourself a sandwich. What changed? Hardware got faster obviously, but software also got more complicated and there are more of them to load up no?

In: Technology

Solid state drives, mostly. The OS is now often put on a solid state drive, rather than a big ‘ol set of spinning platters, from where it can be read into memory very quickly.

Faster processors, but also it’s become standard practice to ship computers with a Solid State Drive for at *least* the operating system. These are a *ton* faster than traditional Hard Disk Drives because they don’t have any moving parts – the computer just goes in and grabs what it needs. They’ve been around for many, many years, just for whatever reason weren’t necessarily the *standard* until the past decade or so.

Nonvolatile RAM memory is another big reason. Meaning it can now save it’s last state when you power down instead of having to reload dll’s and misc drivers everytime you power up. ASICs technology is better and faster as well.

Edit: It’s another really good reason to use the power down command instead of just turning it off in the middle of running/loading a program.

Hardware has gotten so fast that the more complex software’s startup is still nothing compared to what it can do. Especially with SSDs or Solid State Drives, they’re a *lot* faster than modern hard drives, which themselves are a lot faster than the hard drives of yesteryear. You can boot up Windows in just a few seconds, whereas with a typical HDD it can take a minute or two, and even the most beastly set ups from 20-30 years ago it’d take several minutes to boot up Windows versions from back then.

SSDs are the biggest contributor as mentioned, but it’s also due to general OS changes in some cases. In Windows for example, they have “Fast Startup” – which realistically is just waking from a sort of hybrid sleep mode. The computer writes a hibernation file then shuts down, when it boots it does so using that file which is faster than a cold boot.

This is the default in almost all laptops, and in some desktops as well. Any time you boot the computer from “shutdown”, it uses this file which is much faster than normal. A reboot operation is more akin to the shutdown from the old days of Windows, with the caveat that the computer starts back up afterwards. This Fast Startup can be disabled too though.

In the case of Windows since Windows 8 a normal shutdown actually saves a lot of the system state (in RAM) to hard drive. Windows runs upon something called a kernel which is the thing that allows software to run, and it’s state gets saved. This means when starting up there is less to recalculate and fetch from all over the disk (e.g drivers specific to your computer’s hardware), the computer just reloads the kernel from disk and all is good.

A reboot or shut down after an update doesn’t save the kernel to disk and recreates it.

The biggest reason is that we have faster access to hard drives. This is both because we have Solid State Drives, which don’t use physical parts to read/write but instead are purely integrated circuits, and also because we have increased the speed at which data can get between the hard drive and the other system components.

In the days of old, your computer would start up, and it would need to load all the code needed to run the OS into memory, as well as various graphics that are needed for it. This would involve a lot of time spinning around on your hard drive.

Even though modern OS’s use more memory, it can be filled much faster.

In addition, there is also optimizations done in the way things are loaded. For instance, while you might start up Windows 10 bright and fast, it might not cache some graphics or sound files that it will be using until the last steps of startup. This might mean that for the first (very) small while, the OS doesn’t have all the lipstick that you’re used to in normal operation, but that doesn’t affect anything performancewise.

One additional thing is that some applications that run at startup try to not consume resources until you’re mostly idle. If you have something like a game launcher, it might not actually start trying to update your games until after the rest of the OS is started up. In older times, such an application could start working while the OS was still loading, increasing load on the system, and delaying that final OS startup sequence.

Think about making a big, fancy sandwich with a lot of ingredients. Imagine making it in two different kinds of kitchen.

First, imagine making it in a very small kitchen without a lot of tools. You might only be able to get 1 or 2 ingredients out of a fridge at a time, and if you need multiple cooked ingredients like grilled onions or meat you might have to prepare one thing, stop to clean the pan, then prepare the next if you only have one burner. It will take you a very long time to make a fancy sandwich, but it’s possible.

Now imagine you have a very large, professional kitchen. There are multiple stoves, multiple ovens, and tons of countertop space. You can put all the ingredients in an easy place to reach them. You can toast bread, caramelize onions, and grill meat simultaneously. You can make a *better* fancy sandwich faster.

That’s what happened to computers. A long time ago, computers were so limited in what they could do the entire OS couldn’t really fit into memory. So at startup, part would load, it would do some setup tasks, then it’d load more parts, and at some point it’d have to shove some of that work off to a disk to make more room in memory for more stuff. This was very complicated and wasted a lot of time, but computers simply didn’t have the power or space to do better. Today, many people have computers that have more space than they need. So everything can go into memory right at startup and the OS can do all its setup work without swapping things in and out of memory. That’s a lot faster.

The people writing the OSes also streamlined everything too. In the 80s, they’d only had a couple of decades of experience building these systems. By now they’ve had 50+ years to improve upon their techniques.