3.2. Hardware Design Criteria With the functional requirements determined, the next step was to establish design criteria for the mainstream PC hardware. Here are the relative priorities we assigned for our mainstream PC. Your priorities may of course differ.
Silence Is Golden This system is destined to be Robert's secondary office desktop system. His office is already home to four other systems, so it's important that this system contribute as little additional noise as possible. |
As you can see, this is a well-balanced system. Other than reliability, which is of primary importance, all of the other criteria are of similar priority. Here's the breakdown:
Price Price is moderately important for this system, but value is more so. We won't attempt to match the low price of commercial systems built with low-end components, but we won't waste money, either. If spending a bit more noticeably improves performance, reliability, or usability, or if it adds features we want, we won't begrudge the extra cost.
Reliability Reliability is the single most important criterion. A mainstream PC that is not built for reliability is not worth building.
Size Size is somewhat important in the sense that it must fit in an already crowded office, so we don't want the system to be any larger than it needs to be to do its job. So, although we will not compromise other criteria in exchange for smaller size, we will choose the smallest case that meets other system requirements.
Noise level Noise level is at least moderately important for nearly any mainstream PC. Our goal is to build a reasonably quiet PC at little or no incremental cost rather than to build a very quiet PC using expensive special components. Accordingly, when we choose components we'll keep noise level in mind, but we won't pay much extra for a marginally quieter component.
Expandability Expandability is relatively unimportant for a mainstream PC. Fewer than 5% of commercial mainstream PCs are ever upgraded, and those upgrades are usually of a minor nature such as adding memory or replacing a video card or hard drive. Self-built mainstream PCs are more likely to be upgraded, but even then the upgrades are unlikely to require more than perhaps a spare drive bay or two, an expansion slot, or a couple of available memory sockets. We'll choose a case, power supply, and motherboard that are adequate to support such minor upgrades.
Processor performance Processor performance is moderately important for a mainstream PC, both initially and to ensure that the system can run new software versions without requiring a processor upgrade. Midrange mainstream single- and dual-core processors are the "sweet spot" in price/performance ratio. At a given price point, a single-core processor is slightly faster than a dual-core model for people who single-task (do pretty much one thing at a time). A dual-core processor comes into its own on systems like ours that tend to have many windows open simultaneously and many tasks in progress. With a dual-core system, one core is always devoted to the foreground task, so the system doesn't "bog down" under load. Although economy single-core processors like the Intel Celeron and AMD Sempron may suffice initially, spending a bit more on a mainstream processor buys you more horsepower and a larger cache, both of which increase the time during which the processor will provide subjectively adequate performance. The slow and midrange variants of the Intel Pentium D processors are the most cost-effective dual-core processors available. They are aggressively priced and fast enough that you probably won't need to upgrade the processor anytime soon.
Video performance 3D video performance is critical for a mainstream PC only if you use it to run 3D games or Microsoft Vista. Otherwise, integrated video suffices. In fact, current-generation integrated video such as Intel GMA 950 and nVIDIA 6150 is good enough for casual gaming, the Vista Aero interface, and will even support Vista's Aero Glass user interface effects (at the expense of using more shared memory than usual). 2D video quality is important for any mainstream PC, because it determines display clarity and sharpness for browsers, office suites, and similar 2D applications. Intel integrated video provides excellent 2D quality and reasonably good 3D performance. To future-proof the system, we'll choose a motherboard that provides a PCI Express x16 video card slot. That way, we can always add an inexpensive or midrange video adapter if we need better 3D performance or other features not supported by the integrated video.
Disk capacity/performance Disk capacity is unimportant for this particular mainstream system, because it connects to a network that has more than 3,000 GB of available storage. For a standalone mainstream system, or one that connects to a network with insufficient shared storage, disk capacity may be a key consideration. Fortunately, with hard drives currently available in capacities ranging from 80 GB to 750 GB, it's easy enough to accommodate nearly any storage requirements simply by installing one or more hard drives of whatever capacity are needed. Disk performance is unimportant for most mainstream systems in the sense that any standard 7,200 RPM ATA or Serial ATA hard drive is fast enough to avoid noticeable storage bottlenecks for most applications. For those few systems that do require higher performance disk subsystems, a variety of solutions are available, including 10,000 RPM ATA/SATA drives, RAID 0, or, when cost is no object, 15,000 RPM SCSI drives. But standard 7,200 RPM ATA/SATA hard drives are fine for most systems, including this one. For this system, we're less concerned with disk capacity and performance, and more concerned with reliability. Modern ATA/SATA hard drives are extremely reliable, particularly Seagate models, but any hard drive is destined to fail eventually, usually at the worst possible time. When we designed this system, we had just suffered a hard drive crash in one of our secondary desktop systems and spent hours rebuilding and reconfiguring the system, so we had hard drive reliability firmly in mind. In years past, there was no practical, inexpensive way to insure against a hard drive failure. But nowadays, RAID is easy and inexpensive to implement. Most midrange and higher motherboards provide integrated RAID support, so the only incremental cost is the cost of a second hard drive. ADVICE FROM RON MORSE RAID does not insure against hard drive failure. It mitigates/limits data loss resulting from a hard drive failure. In fact, the added drive to support RAID slightly increases the probability you will experience a hard drive failure. <soapbox> And I still contend it is a very narrow attempt to deal with a much broader problem. The idea is to prevent inadvertent data loss. The vast majority of reasons people lose data have nothing to do with drive failure. On the other hand, RAID does complicate installation and maintenance so you do get something for your money. RAID on servers is great. Ought to be mandatory, even. But on a desktop? It promises a false sense of security while dealing directly with only the most unlikely source of data loss. It would be better to hammer home the backup message. </soapbox> |
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