Hardware Reference
In-Depth Information
repair and wait for its return. With a separate system unit and display, it's easy
to repair or swap out the faulty component and have the system back up and
running quickly.
By necessity, we had to choose specific components for our own appliance
system. That allowed us to optimize it for our own requirements, but obviously
your own priorities may differ. Accordingly, we specify numerous alternative
choices, indicating the components that we might have used if we had been
designing the appliance system for a different purpose.
We set our price goal at $350 without the display, external peripherals, or
software—the same as for our budget system. The two systems are very dif-
ferent in their emphases, though. The appliance system makes small size and
low noise the priorities at the expense of performance; the budget system em-
phasizes bang for the buck.
When we sat down to think through our own requirements for an appliance
system, here's what we came up with:
Size
We plan to use a Mini-ITX motherboard, so we looked at Mini-ITX cases
in the 7-liter range (roughly the dimensions of a letter-sized sheet of pa-
per, by about 4” high). That gives us room for a slim optical drive, one 2.5”
hard drive bay with a spare bay for future expansion, and one or two half-
height PCI and/or PCI Express expansion cards. A 7-liter case is about two-
thirds larger in every dimension than a Mac mini case—about five times
the volume—but still small enough to be unobtrusive.
Reliability
One of the major characteristics of any appliance is that it Just Works.
When you click the button on the remote control, you expect your televi-
sion or DVD player to power up every time, day after day, year after year.
That's a bit much to expect from any computer system, so our goal is rea-
sonably high reliability.
Of course, the trade-off here is between reliability on the one hand and
performance and cost on the other. We could design a system with ex-
treme reliability by eliminating moving parts entirely—leave out the
optical drive, use a passively cooled processor and power supply, use an
SSD drive(s) rather than mechanical hard drives, and so on. By doing that,
though, we'd also significantly increase costs, or decrease functionality
and performance, or both. We decided to strike a happy medium here,
shooting for high reliability without needlessly increasing costs or sacrific-
ing performance and functionality.
Performance
We don't expect our appliance system to be anywhere near as fast as
a mainstream desktop system, but we do want enough horsepower to
browse the Web, check email, watch YouTube videos, and so on—all with-
out any noticeable sluggishness. In fact, a system with even half the pro-
cessor and disk performance of the budget system would be more than
