7.1. Determining Functional Requirements The problem with determining functional requirements for an SFF PC is that the SFF umbrella covers a broad range of systems. An SFF PC can be anything from an inexpensive "appliance" PC with a slow processor and embedded video to a fire-breathing gaming systemor anything in between. The only thing these systems have in common is small size. Accordingly, although we had to choose one SFF PC configuration to build for ourselves and to illustrate this chapter, we specify numerous alternative choices in components that we might have used if we had been designing the SFF PC for a different purpose. When we sat down to think through our own requirements for an SFF PC, here's what we came up with:
Size Well, that's the whole point, isn't it? A large SFF PC is an oxymoron. Still, although we wanted a small system, we didn't want to make too many compromises in features, performance, cooling, or reliability. We decided that we'd settle for "medium-small."
Reliability One of our concerns about SFF PCs is that the small case volume makes it difficult to cool the system properly. Running components at high temperatures reduces their service life and makes them less reliable and more crash-prone. The keys to building a reliable system are to choose top-quality componentsparticularly motherboard, memory, hard drive, and power supplyand to keep them cool. In the interests of keeping the system as cool and therefore as reliable as possible, we considered the thermal characteristics of the various components, and chose accordingly.
Performance We wanted our SFF PC to be small, but not slow. High performance goes hand in hand with higher temperatures, of course, so we had to strike a balance between performance and cooling/reliability. Fortunately, new-generation processors draw as little as half the current of preceding models, which makes it easier to use a high-performance processor while keeping the system cool and reliable. We decided that 3D graphics performance was unimportant for our particular SFF PC, so we elected to use integrated graphics. We did, however, want a system that would support a fast 3D graphics card (if we decide to install one later), which meant the case must accept full-size cards and have sufficient cooling to run at reasonable temperatures with a hot-running graphics adapter installed.
Noise level SFF PCs are popular because they are unobtrusive. But unobtrusiveness requires more than small size. A tiny PC that sounds like a leaf blower fails the unobtrusiveness test. The SFF PC must be quiet as well as small. Unfortunately, that introduces yet another trade-off. Quiet PCs are quiet because they minimize fan noise, which impedes cooling, or because they use insulation to deaden sound, which also impedes cooling. Once again, we'll need to strike a balance between sound level, performance, and cooling/reliability. We decided that it was a reasonable goal to build a system that was quiet (but not inaudible) while providing midrange or better performance and reasonable temperature levels. This is a very demanding set of requirements, and one we weren't sure we'd be able to meet. Small, fast, cool, quiet, and reliable. Pick any four. Achieving all five in one system wouldn't be easy. |
