Ask Dan: Fast drives and bumpy fans

Date: 27 April 2007
Last modified 03-Dec-2011.


Hello, pointless upgrades department...

Would a Western Digital Raptor 10,000RPM HDD really make that much of a noticeable difference in general computer operation?

I mainly use my computer for watching DVDs and gaming. It's got a Core Duo 6600, 2Gb of PC2-6400 DDR2 RAM, and a GeForce 7900 GTX.

Would it be worth investing the $AU250 or so in additional storage? Or would I notice quite a bit of an increase by installing my OS onto a 10,000RPM hard drive?


No, the faster drive won't make much of a difference.

The big deal about "server" drives is that they have lower latency. It takes less time for the drive to move the heads to a new piece of data, because the head assembly is faster and/or the physical disks are smaller, so the heads don't have to move as far. And because the drive spins faster, the "rotational latency", when you're waiting for the disk to spin until the data you want is under the heads, is smaller.

When a server's trying to supply multiple clients with data, latency matters. Pure bulk transfer rate can help, too, but high capacity consumer drives are up there with the fastest server drives for transfer rate, thanks to the consumer drives' higher data density.

Both transfer rate and latency make a difference to the operation of a normal desktop PC, but that difference is not nearly enough to counteract the minuses of the high-RPM drives, those being a much worse ratio of price to capacity, and the need for better cooling.

Hard drives run hot because of friction between the spinning platters and the air inside the drive. The faster the platters spin, the hotter the drive gets, all other things being equal. Consumer 7200RPM drives are happy with surprisingly little ventilation, but 10,000 and 15,000 RPM drives need more air flow if you don't want them to die young.

If you're itching for another upgrade, then going from 2Gb of RAM to 3Gb (4Gb is pretty much a waste of money if you're running WinXP and want all of your normal hardware drivers to work) will make a small but probably noticeable difference, especially when you're multitasking heavily (why shouldn't you be able to run Photoshop and Supreme Commander at the same time?). That upgrade won't give you very good value for money even if you've got empty RAM slots to put the new memory in, though; if you have to pull a couple of 512Mb modules and replace them with 1Gb modules, and you don't have another computer to put the smaller modules in, then the upgrade falls into the more-money-than-sense category.

(Another peripheral note about high-RAM WinXP systems: You'll probably need to tweak the system handle and desktop heap settings to be able to use all of your RAM. I talk about this in more detail in this column.)


Speed holes

I'm after a new PSU as my last one got zapped in a storm! I came across the Lian Li HPC-600-A12C power supply on Aus PC Market's site, and I was wondering, do those pitted fans really reduce noise? If so, why aren't all fans pitted?

Do you think this PSU could handle an overclocked Core 2 Duo E6600, GeForce 8800 GTS and about six SATA hard drives?


Do the golf-ball-dimpled fans do anything?

Maybe. But it's probably just marketing.

The sources of fan noise are many and varied. Dimpling the blades can make a difference to only one thing - flow separation.

That's what the dimples on golf balls do - they keep the airflow "attached" to the ball better, so the flow separates less and causes less drag-creating turbulence behind the ball. There's a large difference between the flight distances of dimpled and smooth golf balls.

A fan, however, is not a golf ball.

The ball's trying to slide through the air while perturbing it as little as possible, but it's simultaneously trying to keep itself in the air by means of backspin - all golf clubs put backspin on the ball. These two goals are somewhat opposed; backspin won't work if the ball has zero drag.

A fan's whole purpose, in contrast, is to perturb air, shifting it from one place to another.

For this reason, flow separation prevention devices don't really seem to be much of an idea, for domestic low-speed fan applications (I'll leave transonic jet turbines out of this discussion, if you don't mind). A lot definitely can be done, and has been, to make fan blades more effective - twisted and/or tapered designs, in particular. Even cheap computer cooling fans don't just have flat rectangular paddles for blades.

And yes, there are now more than a few fans with dimpled blades. Here's a company that makes them, for instance. Better flow separation might perhaps make the fan push the air more and twist it less, which could be worthwhile.

From what I can see of the specs for dimpled fans, though, they do seem to be slightly quieter (officially, anyway) than alternatives with similar air-moving specs from other companies (like Delta, for instance). But the dimpled fans also seem to consume a bit more power than the noisier but otherwise equivalent opposition.

There are other variables involved here, though - motor and bearing type, in particular. So I can't make any really firm judgements. All I can say is that there doesn't seem to be a night-and-day difference; the dimples may indeed make a fan a bit quieter, but they also seem to give less air flow per watt.

So feel free to buy dimpled fans, but don't pay a premium for them.

Yes, a power supply with an honest 600 watt rating will be more than enough to run the PC you describe, and then some; feel free to buy the Lian Li one, which is decent value for what you get even if you ignore the super special fan. 600 alleged watts, modular cables, 120mm fan (so it won't be noisy for a given air flow, dimples or no dimples), $AU220 delivered; that's perfectly decent.

(Australian shoppers can order it by clicking here.)

It should still be noted that the sticker wattage ratings for every consumer PSU are at least somewhat dishonest. They either can't deliver their sticker rating at all (well, not with all rails close to their rated voltages, anyway), or can't deliver it for hours on end without something ugly happening.

Lian Li aren't what you'd call a big PSU brand, but they'll be having their PSUs built for them in one of the same selection of Chinese factories that all the rest of the popular PSU brands use. Lian Li will also have ticked enough boxes on the spec sheet - consumer PSUs are pretty much made to a recipe - to end up with a decent product. So the Lian Li "600W" PSU will be about as good as any other big brand's, and that'll give it more than enough power to drive virtually any desktop PC - only the most extreme dual-8800-GTX sorts of systems will overstretch it.

Even small PSU brands like GTR don't lie seriously enough to make their higher-rated PSUs unsuitable to power practically any desktop PC. Any current single CPU, any current single video card, as many drives as you can stuff into a tower case; no problem for a "500W" PSU, let alone a "600W" one.

Australian shoppers can buy the products mentioned on this page from Aus PC Market.