Zalman CNPS9500 LED heatsink/fan

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TESTING

Test Platform

• Intel P4-2.8A The Thermal Design Power of this P4-2.8 (533 MHz bus) is 68.4 or 69.7W depending on the version. As the CPU is a demo model without normal markings, it's not clear which version it is, so we'll round the number off to ~69W. The Maximum Power, as calculated by CPUHeat & CPUMSR, is 79W.
• AOpen AX4GE Max motherboard - Intel 845GE Chipset; built-in VGA. The on-die CPU thermal diode monitoring system reads 2°C too high, so all readings are compensated up by this amount.
• OCZ DDRAM PC-3200, 512 MB
• Seagate Barracuda IV 40G 1-platter drive (in Smart Drive from Silicon Acoustics)
• Seasonic Super Tornado 300 (Rev. A1)
• Arctic Silver Ceramique Thermal Compound
• Nexus 120 fan
• Two-level plywood platform with foam damping feet. Motherboard on top; most other components below. Eases heatsink changes and setup.

Measurement & Analysis Tools

• CPUBurn processor stress software
• Speed Fan software to show CPU temperature
• A custom-built fan controller that allows us to dial in the precise voltage to the fan
• Electronic Anenometer (to measure fan air flow)

Noise measurements were made with the fan powered from the fan controller while the rest of the system was off to ensure that system noise did not skew the measurements. Because the CNPS9500 is sold as an integrated unit with both the heatsink and fan installed, it was tested with the stock fan instead of our usual reference fans.

The ambient conditions during testing were 19 dBA and 26°C. This is about five degrees warmer that is usual in our lab.

TEST RESULTS

Zalman CNPS9500 with Stock Fan
Fan Voltage	Airspeed	Load Temp	°C Rise	°C/W MP	°C/W TDP	Noise
12V	25 CFM	40°C	14	0.18	0.20	37 dBA/1m
9V	20 CFM	41°C	15	0.19	0.22	32 dBA/1m
7V	16 CFM	42°C	16	0.20	0.23	27 dBA/1m
5V	11 CFM	44°C	18	0.23	0.26	22 dBA/1m
Airspeed: Amount of airflow, measured in Cubic Feet per Minute. NOTE: Zalman's specs for CFM were likely taken in free air; ours were taken with the fan mounted in the HS, which means it's facing more restrictions. Hence the lower numbers. Load Temp: CPUBurn for ~20 mins. °C Rise: Temperature rise above ambient at load. °C/W MP / TDP: Temperature rise per Watt, based on CPU's Maximum Power (79W) or Thermal Design Power (69W) rating (lower is better) Noise: SPL measured in dBA/1m distance with high accuracy B & K SLM

12V / 25 CFM: The cooling performance is excellent, on par with the best we've measured. However, the noise level is terrible, with a large amount of turbulence noise and motor whine. The quality of the noise aside, it's simply too loud. 37 dBA/1m will be heard plainly no matter how well damped the case.

9V / 20 CFM: Performance continues to be very good. In fact, there's only a single degree increase compared to the 12V test. Noise drops significantly, although it is still too loud for quiet PC. As before, air turbulence dominates the noise character, although the underlying noise of the bearings and the fan motor can also be heard.

7V / 16 CFM: Here, the fan becomes borderline quiet. This level of noise is probably acceptable in a high performance rig where other components produce too much heat to be cooled more quietly. The whine of the motor is now the predominant source of noise; air turbulence is in second place. Performance is still excellent, dropping only two degrees from 12V.

5V / 11 CFM: The fan drops to a reasonable 22 dBA/1m. This should be quiet enough for many people, although those with low ambient noise may want quieter. A surprising amount of motor noise is still audible as a mid-band hum, and a low buzz from the bearings can also be heard during close listening. Performance is only four degrees off the 12V level. This is exceptional performance with low airflow; many heatsinks lose between 10-15°C of performance when undervolted to 5V.

There is still a considerable performance headroom for quieter operation. This could be achieved through a fan swap (an involved process that requires some handiness), or by further undervolting. The stock fan starts reliably below 4V, although it is difficult to obtain this voltage without DIY skills in electronics.

COMPARISONS

The performance of the Zalman 9500 was compared with its obvious competitors: The Scythe Ninja and Thermalright XP-120, currently at the top of our recommended HS list. For good measure, the original Zalman 7000ALCU was also thrown into the mix.

Two comparisons were made:

• One with constant airflow so we could judge the pure thermal efficiency of the heatsink itself;
• One with constant noise to determine which is best for use in a quiet computer.

Data for this comparison was drawn from the reviews linked to above. All of these reviews use the same testing platform, so measurements are comparable.

Heatsink Comparison at Similar Airflow speed
Heatsink	CFM	°C Rise	°C/W MP	°C/W TDP	Noise
Zalman 9500	25	14	0.18	0.20	37 dBA/1m
Zalman 7000ALCU	23	20	0.25	0.29	39 dBA/1m
Scythe Ninja	22*	19	0.24	0.28	<18 dBA/1m (Nexus fan @ 7V)
Thermalright XP-120	25*	19	0.24	0.28	23 dBA/1m (Globe fan @ 6.8V)
*The Nexus fan CFM was measured directly on the Ninja HS for this comparison. The Globe fan CFM was measured directly on the XP-120 in the previous 7700 review.

The table above makes it quite clear how good the Zalman 9500 is: At roughly the same airflow it significantly outperforms every other heatsink we've tested. However, that is only part of the story. At the tested level of airflow, the Zalman 9500 is far too loud for use in a conventional case. The heatsinks that use 120mm fans have the advantage here because they have a much better noise / airflow ratio than the smaller 92mm fan in the Zalman heatsinks.

Ranking the heatsinks by noise produces a different result, although this is not quite a fair comparison because we were able to choose our favorite 120mm fans for the Ninja and XP-120, while the two Zalman heatsinks were tested with their stock fans.

Heatsink Comparison by Noise
Heatsink	Noise	°C Rise	°C/W MP	°C/W TDP	CFM
Zalman CNPS9500	22 dBA/1m (5V)	18	0.23	0.26	11
Zalman CNPS7000ALCU	22 dBA/1m	27	0.34	0.39	8
Scythe Ninja	22 dBA/1m (Nexus fan @ 12V)	14	0.18	0.20	31*
Thermalright XP-120	23 dBA/1m (Globe fan @ 6.8V)	19	0.24	0.28	25*
*The Nexus fan CFM was measured directly on the Ninja HS for this comparison. The Globe fan CFM was measured directly on the XP-120 in the previous 7700 review.

When the noise level is held constant, the clear winner is the Scythe Ninja, thanks to the quiet 120mm Nexus fan that was chosen. The Zalman 9500 is roughly on par with the XP-120, while the Zalman 7000 is simply not in the same league.

However, holding noise constant does not tell the whole story, either. At 22 dBA/1m, the Zalman 9500 is the quietest it can be in stock form; it is not possible to undervolt its fan any further without resorting to DIY solutions. By contrast, the fan on the Ninja is running at full speed at this level and can easily be undervolted down to below 18 dBA/1m.

It's safe to say that the Zalman 9500 is the most efficient of all heatsinks that use a 92mm fan. The basic design is brilliant, but it cannot completely escape the limitation of fan size. The blades of a typical 92mm fan has only a little more than half the area of those on a 120mm fan. The Scythe Ninja does better at a lower noise level because it has similar fin surface area and can be used with a quieter, larger fan. A quieter fan on the 9500 fan would certainly help, but we suspect it would still not match the Ninja for cooling performance at very low noise levels, simply because the airflow would always be lower because of the smaller fan.

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