Several criteria are critical for us when testing SFF PCs, with two of the most important being noise level and heat generation. A SFF PC device should not necessarily get any louder as it heats up. For that reason the heat loss has to be removed from the case quickly and effectively without a discernible rise in noise level. This should be possible even with a fast CPU. You shouldn't have to forego CPU power just because you're dealing with a small form factor SFF PC. Many manufacturers have attempted to prove this point, yet few have succeeded.
Our most recent test winner, the XPC SB81P showed us what can be achieved. A speedy CPU generally goes hand in hand with higher heat dissipation. But the processor is not the only culprit in raising temperatures inside the case; also doing their bit are fast-spinning hard drives as well as the motherboard chipset, which can get scorching hot.
The following chart shows the heat generated by the XPC SB77G5, measured with the CPU at full load. Even after our two-hour marathon procedure, our noise level measuring device registered just 43 decibels. Measurements were recorded at a distance of 19.7" (50 cm) with a passively cooled AGP 4x graphics card. While not particularly fast, the card is better suited for measuring noise levels than a super-fast Nvidia or Ati model with an active - i.e. loud - cooling solution.