Why games need to load at all
A game is a large set of files held on a storage drive. The processor and graphics card cannot work from those files directly; they work from memory, which is much faster but also smaller and temporary. Before you can play, the game has to copy the data it needs from the drive into memory, and often process it on the way. That copying and preparing is what a loading screen covers.
The amount of data involved is often large. A level can include detailed textures, 3D models, sound, animation and scripts. Loading it all in one go is often the simplest option for developers, and a loading screen is the honest way to tell the player that the game is not ready yet.
How a hard disk drive delivers data
A hard disk drive, or HDD, stores data magnetically on spinning platters. A small arm moves a read head across the platter to the right spot, and the data passes underneath as the disk turns.
Two consequences follow:
- Moving the head and waiting for the right part of the disk to rotate into position takes time. This delay is called seek time or latency.
- Reading one long continuous block of data is quick compared with jumping between many small pieces scattered across the disk.
Games often need many separate files, so the second point matters. A hard drive is typically at its worst when the data is fragmented or spread around in many small chunks.
How a solid state drive delivers data
A solid state drive, or SSD, has no moving parts. It stores data in flash memory chips, and a controller manages reading and writing. Because there is no arm to move, reaching any piece of data takes much less time than on a hard drive, and many requests can be handled at once.
SSDs come in a few forms. Some use the same type of connection as hard drives, and others, often called NVMe drives, connect more directly to the computer and typically offer higher peak speeds. Speed varies by model, and the differences among SSDs are often smaller in practice than the difference between an SSD and a hard drive.
What changes in practice
Moving a game from a hard drive to an SSD often shortens load times noticeably, because the drive was a large part of the wait. How much it helps depends on the game. Some games read a lot of data and benefit a great deal. Others spend most of their loading time on processing, which the drive cannot speed up.
That last point is easy to miss. After the data arrives, the processor often has to unpack it, build parts of the world and prepare it for the graphics card. If that work is the slow part, then a faster drive cannot help much beyond a certain point. Past that point, other parts such as the processor and system memory set the limit, as described in the discussion of hardware bottlenecks.
Because exact figures depend on the game, the drive and the rest of the computer, it is best not to rely on general claims such as one drive being a set number of times faster. Independent measurements of the specific game are more trustworthy.
Streaming and seamless worlds
Some games avoid long loading screens by streaming. Instead of loading a whole level up front, they load nearby pieces of the world in the background while you play, and discard distant pieces. This is common in open worlds, where walking across the map would otherwise mean frequent pauses.
Streaming depends on the drive being able to deliver data quickly and steadily. On a slow drive you may see textures appear late, objects pop into view, or brief stutters when the game cannot fetch data in time. Developers sometimes hide loading behind lifts, doors, narrow corridors or slow walking sections, so the game has time to bring in the next area.
Modern consoles and games are increasingly designed around fast storage, and games built with that assumption may behave poorly on a hard drive. Whether this is true for a specific title is something to check in its published requirements.
Why some games still make you wait
Even with a fast drive, loading screens persist for several reasons:
- Some data must be decompressed and prepared before use.
- Shaders, the small programs that tell the graphics card how to draw surfaces, may need compiling or loading.
- The game may be connecting to servers or checking your save data and settings.
- A level may genuinely contain more data than can be streamed in real time.
For a long time, game media formats such as cartridges and discs also shaped loading, since the speed at which data could be read from the medium limited what developers could do. Now installed storage is the usual source, but the same principle applies.
Practical choices
For most people, a few simple guidelines are reasonable:
- Installing the games you play most on an SSD is a common choice when space allows.
- A hard drive can still be a sensible, cheaper place for large libraries of games you rarely play, or for videos and backups.
- Keeping some free space on a drive helps. SSDs in particular can slow down when almost full.
- Check the requirements listed for a game. Some state that an SSD is recommended or required.
Storage speed will not change your frame rate during play in most cases, because once the data is in memory the drive is mostly idle. Its effect is concentrated at launch, during loading screens and in games that stream.
A short summary
Hard drives and SSDs both do the same job: supplying game data to memory. SSDs do it with far less waiting for the right data to be found, which is why loading is usually quicker on them. A loading screen exists because the data has to be gathered and prepared before the game can use it, and not all of that work is up to the drive.