I’m : a programmer, writer, podcaster, geek, and coffee enthusiast.

Why all computers aren’t as small as laptops

allgrownsup asks:

Can someone please explain to me why it is that you can fit everything a computer needs into the thin bottom half of a laptop, yet desktop PCs are still the size of my torso? It seems like someone (besides Mac) could have made one that is more brick-like by now, but no, HP and Dell just keep cranking out the 90s.

(This is not meant to become a Mac Vs PC thing. I’ve owned and worked on both, and I’m a PC girl. I just don’t understand the lack of form on the behalf of PC designers.)


This is the inside of a MacBook Air’s bottom half. This is about as small as they get — it’s probably even smaller than you thought. The big black thing on the bottom is the battery, which desktop PCs don’t even have. The “computer” part of this is really just the blue circuit board in the upper-right (which isn’t even a complete rectangle — that’s its underside). The foam-ringed white and gray rectangle in the upper-left is the hard drive, and the black turbine-looking thing between them is the cooling fan.

To make it this small, there are a number of trade-offs.

Since there’s very little room for air to circulate, and the fan is very small, every component needs to be selected for minimal heat production. Low-heat parts are much more expensive (mostly because they’re more rare and refined), and they’re usually lower-speed or smaller-capacity than equivalent desktop parts.

Quick tutorial on how hard drives work: A flat disk (or two, or three) spins at very high speeds (between 4,200 RPM and 7,200 RPM for laptops), and a little magnetic head floats as close to the disk as possible to read it — but they can never touch. If the head touches the disk, both get ruined pretty abruptly. (That’s the origin of the word crash — the head crashes into the disk’s surface.) Obviously, this is a fairly fragile setup, but laptops are moved and shocked and vibrated all the time during operation, so their hard drives are made much more durable and tolerant of movement than desktop drives. In addition to the low-power and small-size requirements of laptops, this makes laptop hard drives much smaller, much slower, and much more expensive than desktop drives.

Meanwhile, if you look inside a desktop PC, you’ll find lots of empty space. They’re as large as they are for a number of reasons:

Desktops are much cheaper since they don’t include batteries or monitors, and they don’t need the super-miniaturization that laptops require. And when it comes time to repair or upgrade them (this is a big deal for corporate buyers), they have plenty of room for expansion and they work with cheap, standard parts.

Laptops have some expansion and repair capability, but only for a handful of parts (usually just RAM and hard drives). If a desktop’s monitor dies, you can swap it with any monitor you have lying around in 90 seconds, or you can buy a new one anywhere for $200-500. If a laptop’s screen dies, you have to ship it to the vendor for a week and have them install a new one for $1000.

There’s also the issue of risky users or surroundings. If you spill a drink onto a laptop, you’re completely screwed. But if you spill a drink onto a desktop’s keyboard, you’re out $10. Even if you pour the drink directly onto the tower, it’s unlikely to actually enter any holes. If you’re incredibly unlucky and you pour Coke directly into the exhaust fan holes on the back, and your drink actually hits and kills something on the way down instead of just pooling at the (empty) bottom of the case, you’ll probably only cause $100-300 worth of damage.

So the big honking desktop designs do have some benefits. They’re faster, cheaper, more durable, and more expandable than super-compact (e.g. Mac mini) or laptop designs. And that’s only from what I’ve mentioned here — there are plenty of other situations where desktops still beat laptops.