Brendan Horan Avatar

I will soon be replacing my aging ssh gateway, while the age is not an issue, the noise level is. Its also 2RU. I can achieve all the functions in a much smaller 1RU system this will also save me power and generate less heat.. In this case I will be using my Sun Netra X1, its quite small and I can make it silent.

My Netra is the 400mhz version, I am sure this would also be fine with the 500mhz version. The CPU fan on the Netra is extremely noisy.  Do remember this is "telco grade" stuff so its made not to fail. The fan will start and run and cool the CPU quite fine at 5v with an ambient room temp of 28 to 32 digressed celsius.

The one or two case fans (depending on model) are just normal 40mm fans. Delta.. so there ridiculously noisy. I will replace them withe two Scythe Mini Kaze Ultra 40mm fans, they can run at the full 12v and still are very very quiet no need for 5v on them.

The Netra's LOM will halt boot if it can not find working fans or fans with there RPM to slow. So we need to achieve two things for this mod.

  1. We need a 5v source for the CPU fan.
  2. We need RPM feedback to the two monitored fan headers (CPU and Chassis) note there are two chassis fan headers but only one is monitored.

So what we need to find is a 5v source and a ground source. Pretty easy given the motherboard has a standard 4 pin hdd molex plug on it.

All I did was solder 5v and ground from the back of the board. 1x 5v goes to the CPU fan, 3x ground go to the following : cpu fan and the two ground feedback for the 2 monitored rpm headers on the motherboard.

I then just split the RPM feedback wire into two parts so that each header has a RPM feed going back to it.

You can see from the following images :

  • RED = 5v
  • BLACK = ground
  • BLUE = RPM sensor
cpu-fan-cable

I have the full set of images on this mod. You can find them on my flicker