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Summary
Depending on the heatsink, a 90mm adaptor with a 90mm Delta (86CFM) fan provides between 10%and 20% better cooling performance than the strongest 60mm Delta fan. A rpm regulator can reduce the noise of the 90mm Delta fan to a whisper with cooling performance still on par with the screaming 60mm Delta fan.

The Idea
The idea is simple enough and not new at all: bring the CPU temperature down by using a bigger fan! Sounds easy. But until now we have seen only crude do-it your-self solutions like strapping or even taping a 80mm fan on a 60mm heat sink. For a couple of months now, here in Japan, factory-finished 60mm to 80mm aluminum adapters have been available - we previewed one here. The latest addition is the 90mm aluminum adaptor. The following test should give an idea what to expect from these new adapters when using them with a top performing heatsink and a high-end system.

The Fans
In order to show the maximum possible impact, the most powerful 12V heatsink fans available were used. Such fans are currently provided by Delta Electronics Taiwan. The 3 Delta fans used for this test are outperforming any other fan in their respective size. The 60 mm Delta fan, which was included as benchmark for the best available performance without an adaptor, is a well-known reference product.

These fans are all operating within a range of 7 to 13 volts. The data show that the 90mm is moving almost triple the amount of air through the heatsink as the 60mm Delta fan, which is currently regarded as the must powerful fan for a 60mm CPU heatsink. Although only slightly bigger in dimension the 90mm fan is still moving around 75% more than the 80mm Delta fan. That of course does NOT mean that the CPU temperature is going down proportionally by using this 90mm Delta fan.

The 3 Delta candidates lined up and ready to go: 60mm, 80mm and 90mm fans with shiny fan guards:

Product link: http://www.delta.com.tw/products/dcfans/ffb.htm

The Noise and the RPM Regulator
All 3 fans are running roughly at the same noise level, which is very high and not acceptable for day-to-day use. Although the dB-a is almost the same, the 80 and 90 mm fans are generating noise at much lower rpm. They do not produce the high pitched scream of the 60mm Delta rotating at 6000 rpm. For day-to day use the noise level of the 80mm and 90mm Delta is of course too high. To bring this down, I am using a 3-step rpm regulator from Lian Li (part number C07.01001.02). At 2500 rpm the 90mm Delta fan is just whispering and still proving moving more air through the heatsink than the screaming 60mm Delta fan. It’s always amazing to observe how rapidly the CPU temperature is rising, when the regulator reduces the fan rpm. It also shows drastically how dependent the cooling performance is on the amount of air you move through the heatsink.

The cheap little LIAN LI rpm regulator turned out to be one of my most useful investments recently.

The Heatsinks
In order to show the maximum possible impact, one of the biggest heatsinks currently available was used: the new bi-metal TAISOL CGK761CU-BIG. This is an improved version of the Taisol CGK742092. In order to give everybody a better feeling how the tested adapters would work with a good mainstream heatsink, I included the Alpha PAL6035 MFC, which is more or less in the same performance league like the FOP32. Both heat sinks, the Taisol and the PAL were used with exactly the same adapters and fans and in exactly the same environment. The only exception was that the PAL 6035 MFC was running at 1380MHz, and the Taisol at 1410 MHz, because the PAL was stable only up to 1380 MHz. The core voltage was the same. Product links: Taisol and Alpha.

The feisty Taisol CGK761CU-BIG

The Adapters
Both adapters are made of aluminum, and come form the same source (as I was told by the vendor). The finish is excellent.

The weight is around 100g. The dimensions are 81x81x35mm for the "Downburst 80" and 91x91x40mm for the "Downburst 90 Pro". The bottom design of the 90mm fan is different, because it is part of propriety heatsink combo by this company. The 90mm adaptor is placed half in this heatsink and the turbine like adaptor fins follow exactly the inner design of the heatsink. This combo however is retailing for 11,000 Yen/ 92 USD, and I don’t think it will provide better results than the Taisol CGK761CU-BIG. Product link: http://www.pc-custom.co.jp/

The "Downburst 80" and the "Downburst 90 Pro" solo and mounted

The Asus A7M266 with the 90mm combo mounted on the Taisol CGK761CU-BIG