Impressive!  That's the first word that came to mind when we unwrapped this heatsink.

At 20 cm across, 18 cm high and 1.3 kg on the scales, with a 140 mm fan inside, there are no half measures for the Scythe Orochi.

Apart from its massive dimensions, this heatsink has an unusual form factor.  

To begin with, the part that's actually in contact with the processor looks like the kind of small heatsink that was common in the 90s.

Leaving this mini heatsink there are no fewer than ten heatpipes which transport the heat up to the actual heatsink.

There, heat exchanger has a serious of blades arranged horizontally, rather than vertically as is more usual.

The blades are made from aluminum, and are well-spaced, which is a definite improvement on most traditional models.

Given the size of the whole thing, it's easy to think that the heatsink isn't even using its fan at all.

The fan, though, runs the full length of the heatsink and is 140 mm across.  

Its eleven blades are averagely spaced but fairly small.

According to the specification, it only operates at 500 rpm, which is relatively slow.

We would advise leaving it at its highest speed to make sure it's working the whole time.

Quiet operation

While the fan is running, the Orochi doesn't manage extraordinary performances, but is perfectly acceptable.

Even so, it does an adequate job of cooling both dual- and quad-core processors.

Because the fan turns so slowly, the Orochi is an incredibly quiet processor, even at its highest speeds.

In fact, this heatsink sometimes seems to be running 'passively', that is, without making using its fan.

Life without a fan?

But can it really do without a fan?  According to our tests, ithe answer to this question is something of a mixed picture:

We couldn't complete our investigation using a quad-core processor because the CPU got dangerously hot (well over 80 °C / 180 °F), and that was running with our motherboard exposed on a bench with plenty of ventilation and not stuck inside a case.

Things went a little better with the dual-core processor, where we managed to actually finish the test, but not without the processor getting a lot hotter than we would have liked.

So, if you really do want to try using your heatsink in passive mode, you'll need to make sure you fulfill certain criteria.

Firstly, the case itself will need to be well-ventilated, with a relatively cool processor inside.

That doesn't necessarily mean that the case needs to be noisy, as long as you fit it with quiet fans.

Having said that, though, fitting quiet fans to your case to allow you to use a passive processor heatsink risks becoming something of a false
economy.

In the end, you'll have to decide what leads to a quieter performance: a well-ventilated case with a passive heatsink, or a slightly less well ventilated case and as quiet a heatsink as possible.

It's something of an eternal dilemma to which many a forum post has been devoted …