What is ROM?

 ROM, or read-only memory, is a form of memory that a computer can read but not write onto. ROM is often used to store and play back music (CDs) or movies (DVDs). Unlike RAM, a computer can’t write new data onto ROM, it can only read it, or play it back.

How do I get more RAM without upgrading?

If you’re struggling with low PC performance, or if your computer has only 4GB of RAM or less, the best way to improve computing speed without buying a new machine is to free up your available RAM. There are two ways to get more RAM without upgrading your RAM cartridges:

Close active programs. Any browser tabs you have open (especially in Chrome) or applications you’re running consume RAM. So if you don’t need a tab open or aren’t actively using an app, close it. Only launch what you actually use.

Use Sleep Mode: Our own Avast Cleanup includes a feature that frees up memory by hibernating applications you don’t use. Get Avast Cleanup to free up RAM.

What should I look out for when buying RAM?

The latest generations of DDR4 RAM clock in at around 2,400MHz. Gamers will want DDR4 memory that operates at speeds of around 3,200MHz for Intel chips and 3,600MHz for AMD chips. Other users (such as professional programmers, multimedia editors, and hardcore gamers) may look for higher clocked memory with speeds up to 4,800MHz from specialist manufacturers like G.Skill or Corsair.

Clock speeds are one thing, but another important factor to consider when buying RAM is latency — the time delay between when a command in memory is entered and when it’s executed. The lower the latency, the higher the performance.

For high-level performance, you’ll need memory above 4,000MHz with a latency of around CAS (Column Address Strobe or Signal) 15-18 or less. When buying RAM, you might see this listed as CL 16 (Column Latency 16), for example. For regular users, this is unlikely to make a meaningful impact, but gamers should take note.

And if you want to upgrade RAM on your Mac, ensure it's possible to add RAM to your model before you start shopping. 

Are there different types of RAM?

 Yes, there are multiple types of RAM. As with other forms of computer hardware, scientists are always trying to decrease energy consumption while increasing speed and capacity. RAM has been around since the first days of computing, and in early microcomputing eras it required enthusiasts to plug in chips one at a time. Things have come a long way since then.

By the late 1990s and early 2000s, the main types of RAM were SRAM (static RAM), DRAM (Dynamic RAM), and SDRAM (Synchronous Dynamic RAM).

Today, the most common type of RAM is DDR-SDRAM, or Double Data Rate Synchronous Dynamic Random-Access Memory. And there are various iterations, including DDR2, DDR3, DDR4, and even DDR5.

DDR (double-data rate) allows simultaneous multiple file transfers. The latest version of DDR5-RAM can achieve data rates of about 6.4 gigabytes per second. But supply-chain shortages make DDR5 difficult to get — and very expensive.

The most commonly used RAM is still DDR4 memory, which also comes in multiple types and speeds. Generally, these memory sticks run at or above speeds of 2,400MHz. If you want to squeeze maximum performance out of your memory, you can get higher clocked RAM ranging from 3,200MHz all the way up to 5,000MHz (which is important for gamers and GPU overclockers). The more MHz your RAM has, the faster it runs.

There’s also VRAM (Video Random Access Memory), which is used in graphics cards to process graphical data during gaming, photo editing, or other graphics-heavy activities. Video RAM is even faster than normal memory, and it usually comes in the form of GDDR (Graphics Double Data Rate), which is a specific type of memory optimized for graphics rendering. The latest generation — GDDR6 — can achieve a data rate of 16 Gbps.

Some top-end graphics cards use another type of VRAM known as High Bandwidth Memory — but this type of RAM is hard to find and certainly not cheap.

DRAM vs SRAM

SRAM (static RAM) and DRAM (dynamic RAM) are common types of RAM that each use different technology to store data. Whereas SRAM uses transistors that preserve memory as long as they receive a steady trickle of power, DRAM uses capacitors that need to be periodically “refreshed” by comparatively large bursts of energy every few milliseconds.

The main difference between SRAM vs DRAM based on dynamic capacitors is that while SRAM technology is smaller, faster, and more energy efficient, it’s also much more expensive. For this reason, SRAM is typically used for cache memory, while DRAM is usually used in a computer’s main memory.

Most modern computers now use an upgraded form of DRAM known as synchronous DRAM, or SDRAM. Although SDRAM is much faster than legacy DRAM, it’s still slower than SRAM and consumes a lot of power.