Testing the RX K8 Silent Boost involved several comparisons. I installed the cooler onto a DFI LAN Party main board and Opteron 148 retail processor. The main board and CPU combo had been tested in the Titan Robela water-cooled case (reviewed here). This allowed me to compare both the Robela and RX-K8 in cooling ability and in silent operation, upon which the Robela is partly based. Below the RX-K8 installed on the DFI and in the TITAN Robela.

AMD Test System
CPU	Opteron 148 Retail Socket-939
Mainboard	DFI LAN party UT nF4 Ultra-D
Memory	GSkill HZ PC4000 (2x1024MB DC CL3-4-4-8)
Graphics	Gigabyte GV-NX68T256DH 6800GT
Power Supply	InWin IP-460 460W
Cooling	TITAN Robela water-cooled case Thermaltake RX-K8 Silent Boost AMD Stock Cooler for Opteron S-939
Operating System	Windows XP SP2/3

In addition to comparing the RX-K8 to the Titan Robela and AMD stock cooler I switched out the "reverse flow" 92mm fan with a standard 90mm Thermaltake model TT-9025A. Specifications for the TT-9025A can be seen below.



Compared to the RX-K8's reverse flow fan (PL-2096) which displaces 38.7CFM, the TT-9025A-2B displaces 56CFM. It would seem logical the TT-9025A-2B will produce lower temps and a higher noise level. Below I've installed the TT-9025A-2B installed on the RX-K8.



Test Methods

As mentioned above the RX-K8's performance was tested on the DFI/Opteron combination measuring the CPU core temp using the processor's on-die thermal diode as displayed through Smart Guardian. In addition I inserted a thermistor coming from Robela's on-board temp-monitor LED, between the processor IHS and Heatsink base plate a few mms so not to disturb mounting pressure. The same was true of the Robela's water block. Absolutely no changes were made to the DFI / Opteron test system so that the only variables throughout this test were changing out the Stock AMD cooler for the Robela's water block and exchanging fans on the RX-K8.

To produce a full LOAD effect I used the CPU stress test program S&M 1.7.6. Beta since this test, the version is now 1.8.1.

Ambient temps were consistently between 18~20°C



Sound Level Tests

Since the RX-K8 Silent Boost title denotes quiet operation, sound level tests were indicated. As I stated earlier this was the primary reason I chose not simply to compare this cooler to a H20-system but actually installed the RX-K8 into the TITAN Robela enclosure, thereby minimizing the number of variables. To measure noise levels we use the Intellisystems AR824 SPL meter at a distance of 50cm. Ambient noise level was measured and fixed by turning off all sources of noise and taking measurements during the evening hours. For our purposes the figures below show dBA levels over ambient.



Thermaltake has utilized the fan found in our RX-K8 with the Mini-Typhoon which our Editor reviewed here. While I didn't exactly find the RX-K8 to be dead silent I still felt it met the criteria for "silent" cooling. Of all the reviews we researched on the RX-K8 and Mini-Typhoon there were quite a bit of mixed results.

As I stated in the introduction, the reviewing/testing community on the whole lacks the capability to perform truly accurate, objective sound measurements. This goal will be nearly impossible to achieve without constructing an anechoic chamber. For those interested in the cost and complexities involved in building an anechoic chamber, this article on McIntosh anechoic chamber is a MUST read. If there are degrees of accuracy among anechoic chambers (which there are), imagine the inaccuracy among ad hoc tests performed in most reviewer's homes? For this reason the best method I could come up with was to measure the ambient noise in my room then record the increase in sound (if any) the device in question produces. If your ambient sound level measures 30dBA and you find a particular HSF emits 60dBA , essentially your proposing the HSF being tested emits 30dBA above ambient. Since this is always an approximation based on an infinite number of variables we should treat these figures with relative skepticism.

Summary

PRO
Silent Operation.
Decent Overclocking ability.
Easy Mounting system.
All copper construction.

CON
Mounting Limited to AMD.
A more powerful fan with rheostat would be preferable.

Price at time of writing: Thermaltake's RX-K8 Silent Boost can be found through FROOGLE at numerous shops for as low as $27.00.

Conclusion

Thermaltake RX-K8 Silent Boost is an HSF which offers a slightly higher level of performance under slightly less noisy operation. As we've seen, several reviews had the RX-K8 producing 40dBA+ running flat out, which is fairly noisy. This is also the reason I choose to eschew testing and measuring performance using a motherboard fan-controller program. Had the RX-K8 came with a rheostat I would have measured temp/noise-levels at different speeds. As it stands the degree of variance from one motherboard BIOS fan-controller to the next is simply too great for my figures to be applicable, not to mention the number of people who don't even bother to enable these programs.

The RX-K8 as is, won't appeal to Overclockers although I was able to overclock the Opteron 148 as high as 2750MHz. Since this involved raising Vcore I've only included overclocking data at default Vcore. In the final analysis I believe the tendency to focus on the "Silent" in Silent Boost leads us astray from the real benefits this cooler has to offer. Thermaltake has built a high quality copper cooler with substantial surface area; proof of this can be found where its original fan was substituted.

Can I recommend this cooler? To be honest it depends on what you’re looking for, there are better alternatives at the same price in silent category and in the overclocking category. If this HSF were sold with a more powerful fan and a rheostat I wouldn't hesitate to recommend it, if you can find the RX-K8 for under $25 I would recommend it.

Questions/Comments: forum thread