Cool bananas

Originally published 2002 in Atomic: Maximum Power Computing
Last modified 03-Dec-2011.


Overclockers have a bit of a... thing... for cooling.

Air cooling. Water cooling. Recirculating vapour phase cooling. Non-recirculating Esky-full-of-liquid-nitrogen misty-floor cooling.

It's not a fetish. It's a romantic abnormality.

The official reason for all this is simple enough; better cooling equals more overclockability.

The faster you run gear, the hotter it gets. A given chip will increase in heat output linearly with its clock speed, and roughly with the square of its core voltage. So a 25% overclock with a 25% voltage boost means almost twice as much heat. If you don't get rid of that heat, you'll let the smoke out of your chip. Which is a leading cause of tweakers Having One Of Those Conversations with a retailer on the subject of warranty replacements, and how CPUs that have been hot enough for all of the on-chip components to have melted their solder and fallen off probably did not get that way because of a manufacturing defect.

Heat versus speed is not a simple two-variable game, though. You may be able to get, say, a 2.8GHz P4 to 4GHz with the help of liquid nitrogen, but that doesn't mean you'd be able to push it up past 5GHz by pouring liquid helium on it. There are hard limits to how fast transistors can switch, at any temperature.

As I write this, the top-scoring nutballs are getting about 4.4GHz - 4.6GHz, at most - out of P4s. They mainly use the 3.06GHz model, which is the current flagship, but this is with cryogenic cooling that's no use for normal PCs. Liquid nitrogen and dry ice shenanigans are not unlike adding a nitrous oxide injection system to your car. Great on the drag strip, sure, but not helpful in daily driving, unless you're up against the last of the V8 interceptors.

Cooling systems that you can use in an actual regular PC - generally water-block systems with or without Peltier devices, or vapour phase systems of one kind or another - don't score quite as well.

Meanwhile, people with air coolers - often the rather powerful stock air cooler, in a reasonably well ventilated case - are managing 3.5GHz or better from 3.06GHz P4s.

The most an overclocker with an actual PC that can do normal things can expect, therefore, is around 1.2 times the performance they could have got with a simple air cooler. That's all you can get, no matter how much you pay for your CPU cooling rig.

It's clearly not sensible to invest in ludicrous active cooling equipment - the currently-hip Prometeia vapour phase system will set you back well over $US600 - just to get another 20 or so per cent CPU speed.

All this, of course, is missing the point.

People who hunt that ultimate few per cent aren't doing it because it's vitally important to them that their game frame rate, 3DS MAX render time or spreadsheet recalc be that much faster. They're doing it because they can, and/or for bragging rights.

At first glance, this looks like just another boys-and-their-toys situation. Until you notice the billion dollar companies that're doing the same darn thing.

Intel and AMD (market capitalisations about $US117 billion and about $US2.3 billion, respectively, as I write this) have been engaged in a gorilla-versus-chimp slapfight over the PC processor speed crown for ages, now. AMD had the edge for quite a while but Intel now back in the running. The speed difference between flagship Athlons and P4s, ignoring price, has never been enough that users would be likely to notice it for most tasks. But apparently that doesn't matter.

People who'll pay twice as much money for the top-of-line CPU, when the next one down is only 10% slower, need to be wrapped up in damp felt and left in a shady place to calm down, if you ask me. Peak speed of the flagship chip is hardly the most interesting feature of either company's CPU range.

But flagship chip speed is, apparently, the only thing they think Joe Average is likely to care about. So that's what all the press releases seem to be about.

I presume this is also why Ford and Holden reckon that sticking totally non-standard simulacra of their top-of-range vehicles on racetracks will push along sales of the six cylinder squishy-suspensioned fleetmobiles.

If you can manage to avoid this obsession with knowing your PC's a bit faster than the next guy's - you can't really see the difference, of course, but you can still measure it - then you've got an advantage.

And you still have the opportunity to show off.

If you want to make the side of your case a square array of a hundred 40mm fans, go right ahead and do it - safe in the knowledge that fewer, larger fans would actually deliver more air, but that the tiddly ones look more entertainingly like electronic chicken wire protecting the illuminated Blues Brothers figurines standing on your video card from the caffeinated beverage vessels hurled in your direction by the less 1337 LAN party attendees.

Authentic ambience can be provided by a car cigarette lighter, running from the PSU's 12V rail, with a small peristaltic pump dripping commercial glycol smoke fluid onto the element.

You can pay for the fans and other decorations with the money you save by not buying the gold-trimmed flagship CPU, top-spec max-clock video card, and officially-blessed-by-the-Dalai-Lama RAM modules. Just don't. And, if you must, say you did.

Like a fiancée who's pretending that the three carat cubic zirconia on her finger's a real diamond, while the money that would have been spent on the rock's actually gone towards buying a house, it can be your little secret that your hardware is actually last month's fashion.

If being the tweakiest gunslinger in town is your thang, then you probably are going to buy top-of-range hardware and upgrade pathologically often. There's really nothing else for it.

But if you're in it for the fun of it, then your money will be better spent on 125 disco-ball key-rings to hang all over the case, a dozen laser diodes arranged around the top, and a windscreen wiper motor built into the base to jiggle it all around.

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