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Practical Computer Advice
from Martin Kadansky
Volume 16 Issue 5
Why Is My Computer Slow? What Can I Do About It?

The Problem
Computers can run slowly for any number of reasons, ranging from simple (running low on critical resources, external causes, heat, temporary glitches) to somewhat complicated (software or hardware problems) to very complicated (multiple reasons, no obvious causes). Improving or solving a slow computer can also involve a range of approaches, depending on the problems, your time, and your budget.
Back in the early 1980s when I started my previous career as a software engineer, my boss taught me a valuable lesson: Don't assume that you know what is causing a system to be slow. Instead, you should observe, measure, and keep an open mind.
Read on for a brief survey of many of the reasons why a computer might be slow. Details on how to diagnose and solve such problems are beyond the scope of this article.
Things to pay attention to
Does your computer run slowly:
  • Only when you're using certain programs, but not others?
  • Only when you're using internet-related programs (most often email and web browsers)?
  • Only at certain times of the day?
  • Only just after it's started up? Only later, after it's been on for a period of time?
  • All the time, regardless of what you're doing?
  • When did the problem start? Only after you started doing something new (like using a new program or service), or ever since you bought the computer?
The first thing to try
If your Windows or Macintosh computer is running slowly (or acting strangely in other ways), it never hurts to save and close all of your work and then Restart or Shutdown; do not use Sleep or Hibernate nor just close and reopen the lid if it's a laptop. Turning it off and on again may clear up the problem, but since that's not a long-term solution, pay attention to how soon it returns.
Not having enough memory (RAM)
You can think of memory as the area where your computer copies in the programs from your hard drive that you open (as well as various parts of the operating system) in order for your CPU to run them. Metaphorically, you could imagine taking a file of papers out of your file cabinet and spreading them out on your desk to get some work done.
As long as you have more memory than is needed by all of the programs that you're using at any one time, this is an efficient system. However, if the need goes beyond that, a "virtual memory" system gets triggered, which uses a portion of your hard drive as an "overflow" or "swap" area. Metaphorically, if you ran out of room for active project papers on your desk, you could imagine temporarily parking some of those papers on the floor before taking more papers out of your filing cabinet and putting those on your desk to work on.
The ability to employ virtual memory enables your computer to run more software than would fit in memory, but the "cost" is usually a major slowdown in the speed of the computer, as some programs are "swapped out" of memory to the hard drive and others are "swapped in" from the hard drive back into memory.
In general, one low-cost solution to this (compared to buying a new computer) is to add more memory to the computer, if possible. Unfortunately, the memory in some computers is soldered onto the motherboard at the factory and cannot be upgraded later.
Your CPU (or GPU) has too many demands on it
You can think of your computer's CPU (central processing unit) as the "brains." Like a person who can only do so much at a time, the more software (or hardware) that demand your CPU's "attention" at the same time, the longer it can take to get things done, and the more sluggish the computer may feel to operate.
Your computer's GPU (graphics processing unit) can sometimes be part of this issue as well, especially if you're trying to use software that has higher requirements (or recommendations) than your current hardware, e.g., sophisticated graphic design or photography programs.
Your computer's CPU (or GPU) probably cannot be upgraded.
Your hard drive gets overloaded with demands, or is nearly full or failing
Competition: If two or more of the following occur around the same time:
  • You begin copying many gigabytes of data to an external drive.
  • Your scheduled antivirus scan starts.
  • A software update starts downloading and installing.
  • Your scheduled backup starts.
then that can noticeably slow things down until one or more of those competing tasks finishes.
Disk full: Of the hundreds of computers I've seen since I started my business in 1998, I've probably only seen about 5 or 10 whose hard drives were nearly full, i.e., more than 95%. For some reason (my guess would be the number of icons on the Desktop) many other people have thought that theirs was full, but after measuring I found that they actually weren't.
Your computer often needs to create temporary files while it's working, and relies on the hard drive to have a certain amount of free (unused) space to do that. A very-full hard drive has very little free space, which can slow that process down a lot or cause other problems.
Disk failing: If your computer is having trouble reliably reading data from (or writing data to) certain spots on its hard drive, it will try over and over to read (or write) that data. Much of the time those retries eventually work, but that repeated effort takes more time.
If the capacity (or speed or reliability) of your hard drive turns out to be a problem, with a bit of work it can be replaced with a newer, larger-capacity, and faster one. The ultimate speed upgrade is to go from an older "rotational" (motor-driven spinning-platter) drive to a solid-state drive (SSD), although the cost-per-gigabyte for SSD drives is higher.
Your internet connection or network is slow
Since many of the things you do every day probably involve the internet (and therefore also your wireless or wired local network), any issues with any component of that infrastructure can affect the speed of your computer. This includes:
  • The web site or server you're trying to access is having problems or overloaded.
  • Problems with your computer's Wifi network card (or your wired network card or port)
  • Competition from the other computers and devices connected to your local wireless (or wired) network
  • Issues with your internet modem and router (or combined gateway), access points, network extenders, switches, wires, etc.
  • Glitches with your virtual private network (VPN) software or hardware, if any
  • Problems with the speed of your internet service
  • Issues with your internet service provider (ISP)
Any of these problems can slow down your effective internet speed.
Your computer is overheating
When it's running, the temperature inside your computer is much warmer than room temperature. In my experience it can be anywhere from 110 degrees Fahrenheit to 170, with laptops running hotter than desktops. Unfortunately, the very mechanism designed to keep your computer cooler (its exhaust fans) can lead to it overheating, possibly to the point of hardware failure. As the fan pulls in cooler room-temperature air on one side and expels warmer air on the other, it also pulls in dust, pet hair, pollen, carpet fibers, cigarette smoke, etc., not all of which makes it out the other side. That debris can slowly form a "blanket" on your motherboard, preventing the fan from cooling it. When a computer overheats, it can run slowly and exhibit other erratic behavior.
I recommend having your computer checked for accumulated internal dust every 1-3 years, ideally by a professional (or someone skilled enough not to damage it as they take it apart to look) who would then use compressed air (not a vacuum cleaner) to blow out the dust.
Multiple causes
Many of the resources inside your computer are interrelated. Most tasks involving your hard drive also require CPU and memory. Not having enough memory can trigger the virtual-memory mechanism, which requires additional CPU and hard drive resources. Downloading files from the internet or sending and receiving email involve your CPU, memory, and hard drive as well as your local network and internet connection.
Other possible causes
Going beyond what your computer can handle might include:
  • Opening too many programs at the same time
  • Trying to use software that really requires a newer computer than yours
  • Upgrading to a newer operating system without first checking whether your computer can run it well
Less-common reasons for a slow computer can involve almost anything and affect everything:
  • Software: Incorrect settings, corrupted or missing program elements or drivers
  • Hardware: Bad memory, faulty power supply or other internal hardware, bad internal wiring or external cables
  • Peripherals: A bad or failing mouse, keyboard, printer, USB hub, modem, router, network device, etc.
Short-term workarounds
Here are a few things that can help in the short term:
  • Restart
  • Close windows and programs that you're not using at the moment
  • Limit the number of programs that you open at any one time
  • Make sure that scheduled, computer-intensive processes don't happen at the same time, including antivirus scans, software updates, backup, etc.
And as always, if this is too complicated or confusing for you to deal with on your own, I recommend that you ask someone that you know and trust to help you.
Where to go from here
  • google: why is my computer slow
  • google: how avoid virtual memory
  • google: why is my hard drive slow
  • google: hard drive speed rotational vs. ssd
  • google: why is my internet slow
  • google: why is my wifi slow
  • http://www.kadansky.com/files/newsletters/2009_10_21.html - "Should I leave my computer on, or turn it off?"
How to contact me:
phone: (617) 484-6657

On a regular basis I write about real issues faced by typical computer users. To subscribe to this newsletter, please send an email to martin@kadansky.com and I'll add you to the list, or visit http://www.kadansky.com/newsletter

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I love helping people learn how to use their computers better! Like a "computer driving instructor," I work 1-on-1 with small business owners and individuals to help them find a more productive and successful relationship with their computers and other high-tech gadgets.

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