Thursday, June 30, 2011

What's the Deal With CPUs?

Welcome, friends, to another episode of Andrew Explains Stuff To You. This week, our topic is processors! Computer processors, I mean, not food processors or word processors - this week I'm all about the Pentiums.

Computer processors are mysterious things. They have to be relatively efficient at processing everything from typing to streaming video to image editing to gaming, and they've got to keep getting better at it while also consuming less electricity and taking up less space. This all ties into something called Moore's Law, which you should totally read about.

While the fundamental architecture of a given computer's Central Processing Unit is the same now as it was three decades ago, its efficiency has increased dramatically, and what's coming down the pike is only going to change it more drastically. This is going to enable all of the tiny, speedy computers that you'll all be buying in the next few years, and this post is all about what's enabling that technology.

The End of the MHz Race

For computers, the aughts began much differently than they ended - the early 2000s saw the tail end of a near-pointless speed race that saw every 33 MHz increase promoted and dissected ad nauseum by both computer manufacturers and the tech press, while the end of the decade saw advances marked by reduction in size and power usage just as much as increases in speed.

The early-decade MHz race ended mostly because of the Pentium 4, a highly-popular but highly-not-that-great chip from Intel. By design, it was less efficient (i.e., a Pentium 4 at 1.4 GHz would actually be outrun by a Pentium 3 at the same speed), but it was designed to go so much faster than its predecessor that the inefficiencies would be nullified. The Pentium 3 topped out at 1.4 GHz, but the Pentium 4 was expected to reach speeds at and above 10 GHz over time.

These processors actually topped out at just under 4 GHz, due largely to power consumption and heating problems, and Intel was left with a problem: if speed couldn't be increased by conventional means, how best to continue the relentless march of technology?

Increasing Performance Without Increasing Speed

The answer turned out to be something that Intel's primary competitor, AMD, had been doing for awhile - first going for more efficient processors rather than processors with high clock speeds, and then by making a move to 64-bit processors (which theoretically allow for increases in the speed of software execution, but in reality are more useful for their ability to work with more than 4 GB of RAM). Using these methods, AMD began to slowly chip away at Intel's almost Microsoft-like marketshare in the early-to-mid 2000s.

Another innovation that began to show up in 2005 and 2006 was the dual-core processor - no matter how fast your processor was, it could still get hung up doing one very intensive task (editing video files, for instance). A dual-core processor solves this by giving your software what is basically a second processor to work with, meaning that properly optimized software can run twice as quickly, and that one processor core can continue doing work if the other is tied up with heavy lifting.

The good thing about the dual (and triple, and quad, and etc.) core processor is that it doesn't require a bump in clock speed to be faster than a single core model, meaning that you can avoid some of the extreme power consumption and heat issues that Intel ran into as it tried to speed up the Pentium 4. The bad thing is that you're still putting multiple processors in the same amount of physical space that used to house only one, so if your processor is innately hot and power-hungry, you'll run into problems anyway.

So, in 2006 and 2007 Intel rapidly abandoned the Pentium 4 in favor of Core Duo and Core 2 Duo systems (based, interestingly, on heavily modified Pentium 3 designs), which were both more efficient and possessed of multiple cores.

Not Just a CPU Anymore

Since then Moore's Law has continued unabated, giving us new processors every year that are either faster or more power-efficient or both. To really reduce space, though, you have to cut down on the number of chips a computer needs, which is what processors are doing in the present day.

A computer at the beginning of the decade needed four basic chips to function: the CPU (which we've spoken about), the graphics processor, the southbridge (which handled communication between hard drives, USB devices, and other peripherals and the rest of the computer) and the northbridge (which handled communication between the CPU, GPU, and system memory).

The first of these chips to begin disappearing was the northbridge - AMD began incorporating its functionality into the CPU itself as early as 2003, and Intel systems began doing it just a couple of years ago. Now, increasingly, the GPU is being included on the CPU package as well, either as a separate chip (some Intel designs, see above) or grafted on to the CPU itself (more modern designs from both AMD and Intel). If you need a more powerful graphics processor for gaming, you'll still need a separate GPU, but today's integrated GPUs are becoming increasingly useful for low-end games, media playback, and certain types of specialized work.

Combining all of this into one package has two benefits: the first, obviously, is that the fewer chips you need to make room for, the smaller you can make your device (smartphones and tablets, as a rule, have one main chip inside them that handles most functions). The second is that having all of this technology in closer proximity reduces the amount of time it takes for them to communicate, reducing latency and improving your computer's speed.