Listen to the mind-numbingly repetitive radio programming on the FM dial long enough, no matter which genre you prefer, and you might conclude that only a handful of recording artists are worth listening to.
Fire up your PC and tune in to Internet radio, on the other hand, and you’ll discover an embarrassment of riches, nearly all of which you can enjoy for free and without—or at least with very little—commercial interruption. In fact, there’s so much music that you might find yourself overwhelmed. That’s where the music discovery services Last.fm, Pandora, and Slacker come in. All three services help you discover new music based on the songs and artists you express a preference for. As interesting as that concept is, what’s even more remarkable is that each service takes a completely different approach to the mission. Let’s take a look at all three.
Can a computer exist without hardware? It can if it’s a virtual machine. A virtual machine is software that’s capable of executing programs as if it were a physical machine—it’s a computer within a computer. Virtual machines can be divided into two broad categories: process virtual machines and system virtual machines.
A process virtual machine is limited to running a single program. A system virtual machine, on the other hand, enables one computer to behave like two or more computers by sharing the host hardware’s resources. A system virtual machine consists entirely of software, but an operating system and the applications running on that OS see a CPU, memory, storage, a network interface card, and all the other components that would exist in a physical computer. For the remainder of this discussion, we’ll use the term “virtual machine” to refer to a system virtual machine.
Software running on a virtual machine is limited to the resources and abstract hardware that the virtual machine provides. Since a virtual machine can provide a complete instruction set architecture (ISA, a definition of all the data types, registers, address modes, external input/output, and other programming elements that a given collection of hardware is capable of working with), a virtual machine can simulate hardware that might not even exist in the physical world.
Using virtual machines, a computer can run several iterations of an operating system—or even several different operating systems—with each OS isolated from and oblivious to the existence of the others. The only requirement is that each operating system must be capable of supporting the underlying hardware. And, of course, there must be enough resources (memory, hard disk space, CPU cycles, and so on) to support everything. You could use a virtual machine to run Linux on top of Windows, for instance, or you could run two versions of Windows and use one as a sandbox for testing software you wouldn’t trust on a “real” machine.
In the immortal words of Buckaroo Bonzai, “Wherever you go, there you are.” But if you want to know precisely where “there” is, you need a GPS device. Let’s examine how this technology operates.
The fundamental idea of a satellite-based navigation system was conceived prior to Word War II, but no one pursued the idea aggressively until the Russians launched Sputnik, the first artificial satellite. Research continued through the 1960s, and the U.S. Department of Defense settled on the first design in 1973.
The first developmental GPS satellite—Navstar 1—was launched in 1978, the first fully operational GPS satellite was put into orbit in 1989, and the system was declared fully operational in 1995. Although GPS remains an indispensable military tool (and is maintained by the U.S. Department of Defense), the technology was made available to consumers in the 1980s and can now be found in relatively inexpensive devices ranging from cellphones and PDAs to dedicated handheld GPS receivers.
In one second, the nuclear fusion process taking place inside the sun produces enough energy to satisfy the needs of the earth’s population for nearly 500,000 years. Photovoltaic cells are capable of capturing some of that energy and converting it into usable electricity; unfortunately, today’s technology can’t do this very efficiently.
French physicist Edmond Becquerel first described the photovoltaic effect in 1839. He discovered that some materials were capable of producing small amounts of electricity when exposed to sunlight. The first photovoltaic cell, however, wasn’t created until 1883, and more than 70 years passed before the next major scientific advance took place, when researchers at Bell Labs developed the first crystalline silicon photovoltaic cell in 1954.
We invariably refer to the video memory in modern videocards as GDDR, differentiating it only by version (GDDR2, GDDR3, GDDR4, and now GDDR5), but the technology’s full acronym is actually GDDR SDRAM, which stands for Graphics Double Data Rate Synchronous Dynamic Random Access Memory.
“Double data rate” describes the memory’s capacity for double-pumping data: Transfers occur on both the rising and falling edges of the clock signal. This endows memory clocked at 800MHz with an effective data-transfer rate of 1.6GHz. “Synchronous” refers to the memory’s ability to operate in time with the computer’s system bus. This allows the memory to accept a new instruction without having to wait for a previous instruction to be processed, a practice known as instruction pipelining.
The shiny, new hatchback you nudge in a street race dents slightly on the driver’s side door. Although you’re playing a PC game, created with beaucoup equations, the bend looks almost real. The 3D renderer sculpts all those numbers into images, with help from the video API (application program interface). However, several completely different rendering techniques can be the source of those images. Currently, the hardware and software industries are debating how to best utilize two graphics-rendering techniques: ray tracing and rasterization.
Hit the jump to see how 3D game rendering is changing with hardware advancements.
We tend to take things for granted when they work exceptionally well. Take Ethernet, for instance; it’s almost magical: Plug a simple cable into a computer, and it can exchange data with another rig—or many others. Peek behind the curtain and you’ll discover a brilliantly simple yet continually evolving networking system.
But let's make one thing clear: Ethernet technology doesn't actually contain ether.