Two Minute Tech Talk: Things You Should Know about CPUs

By nature of my degree (Computer Engineering), I have been forever addressing the questions friends and family have about computers.

By nature of my current role, I get to talk a lot more about (arguably) the most important part of the computer: the processor.

The processor, commonly called the CPU (Central Processing Unit), is at the heart of your laptop, desktop, server, smart phone, smart "thing". For purposes of this writing, let's focus on the type you find in a laptop.

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Sidebar: A Brief History

How long would you guess processors have been around?

It's important to note that this technology was predated by some significant technology steps:

the invention of the transistor and the invention of the integrated circuit.

A transistor is a miniature electronic component that can do two things: amplify and switch an electric signal. Transistors are the basic building block that lets computers store information and make decisions. In 1947, John Bardeen, Walter Brattain, and William Shockley invented the first transistor at the Bell Laboratories and then patented the technology in 1948.

The integrated circuit followed in 1958: this nifty advance puts a bunch of transistors together in a complete logical circuit and miniaturizes it onto the surface of a piece of silicon. This is actually a pretty interesting time of computer history as two brilliant dudes filed almost identical patents for the IC only a couple of months apart (Jack Kilby at Texas Instruments and Robert Noyce at Fairchild Semiconductor). I won't go into the nitty gritty here, but in short, these guys are jointly credited with the invention, but I doubt either is happy about that situation :)

Officially, Intel launched the first microprocessor in 1971 - the Intel 4004. It had 2,300 transistors, performed 60,000 OPS (operations per second), addressed 640 bytes of memory, and cost $200.00.

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So! You're in the market for a laptop, I hear. How do you go about picking the right processor for your needs?

Processor specifications: The Big Three

If you're sitting in on a sales roadmap, you'll hear a lot of numbers associated with the processor. Here's what they are and what they mean - and I want you to be able to answer the question above: Does more of this feature mean a better processor?

ONE: CORES

This is a hardware term that describes the number of independent central processing units found in a single chip. Originally, you only had one core, but now it's common to see dual- and quad-core CPUs. Generally, more cores means better performance; with a single core, the processor performance is bottlenecked by the time it takes to communicate with the Cache and the RAM. Multiple cores allow the computer to run multiple processes simultaneously, which makes a big difference if you intend to multi-task or use power-hungry apps.

TWO: THREADS

A thread is a string of data from a program that goes through the processor. If you are multitasking (i.e., typing up comments in response to this blog while calculating something in Excel), the computer core must switch (quickly) between threads created by each application to get your stuff done. Once again, more threads generally means better performance, but it also depends on your application! There are certain applications that really take advantage of multiple thread capability, and others that simply do not. This is an important question to ask yourself: How does my application work within the computer?

• Technically, a core can only handle one thread at a time, so thread count in excess of core count is an engineering trick... and I'm not prepared to whip out my old textbooks to talk about concurrency and parallelism. So your takeaway is: More threads, probably better, but depends on application :)

THREE: FREQUENCY

The higher the frequency, or clock speed, the faster the core can retrieve and interpret instructions. This is measured in gigahertz (GHz), or billions of cycles per second. Before multiple cores came around, clock speed was the definitive spec for comparing processor performance. Nowadays, multiple factors come into play, including which architecture the CPU was built on. An older architecture probably has a different instruction set that may handle things less efficiently than a new one; however, frequency is still a pretty good metric to compare processors of the same generation.

• A note on overclocking: a lot of gamers out there (you know who you are and you probably aren't reading this article) like to speed up the clock past its rated limit to get improved performance - but this comes at a cost. It pushes up the amount of heat produced by the device (heat is the enemy of electronics) and can void the warranty.

Additional specifications

TDP

Thermal Design Power is the maximum amount of heat generated by the processor when it's working the hardest it can. It's also often used as a basic indicator of how much power the processor consumes. More watts often mean better performance - but remember, heat is the enemy, and higher watts mean higher temperatures. They also mean a reduced battery life for your laptop.

CACHE

Every processor has some built-in "scratch space" that serves to speed up access to data and instructions between the processor and the memory. The cache size will be specified in MB.

MEMORY SPECS

Remember when I talked about storage vs. memory? In a processor, there are actually limits to how much RAM the CPU can support, as well as the type of memory it can support.

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Confused? Don't be. Think back to The Big Three: Cores, Threads, Frequency - and consider your workloads to make the right decision.