Thursday, December 3, 2009

Rooter Hardware

Rooter - British pronunciation of router. This is post describes the hardware in my Atom router.

I wanted a low power x86 router. There a number of things that I want to be able to do with it on my lan: DNS for naming/tracking a few dozen devices, VOIP, media serving with MPD + PulseAudio.

I choose Atom because it is cheap to buy and to run. CPU/Mobo combos start at $50. There are two flavours of Atom boards: cheap ones with desktop chipsets and more expensive ones with laptop chipsets (which consume 50% less power). I also needed to have 2 nics and to have gigE on the LAN side. Most boards ship with RealTek NICs which have absolutely terrible drivers. Unfortunately there is only one (MSI IM-955GSE-A) massmarket dual Intel-gigE board that doesn't suck and it costs $150.

Due to a misleading ebay listing I ended up buying MSI IM-955GSE-B on Ebay. It is the former boards' wierdo industrial sibling(no VGA, 1 gigE, but 6 serial ports!). It features a builtin DC2DC power supply which connects via a floppy-power-connector to a 12V DC source.

To make up for a missing Ethernet port I opted for a USB2.0 100Mbit nic (Trendnet TU2-ET100,which uses the 'asix' driver). This NIC is a true full-speed device and easily sustains 11MB/s transfers, so it's perfectly good enough for a WAN port.

I got the cheapest Mini-ITX case on ebay. It came with a great 65W Seasonic power supply.

Case - $30
Mobo/CPU - $82
2GB RAM - $30
USB NIC - $18
Total: $160

I installed Fedora onto a spare 4gb usb stick. I am really happy with the resulting computer. It is very quiet because it has no moving fans.

PSU Hack
Current 13W idle power draw is reasonable given that the PSU is likely underloaded and thus less efficient .
Currently, the mobo is powered by shorting the ON pins on the PSU(+ducttape for robustness) and a custom Molex2Berg adapter cable(made for me by a very resourceful friend). Eventually I plan to switch over the EEE power supplies as they are better specced for such low power motherboards. This would also avoid redundant dc2dc conversion going on in the case.

Power-On AC
I considered using busted netbook for rooter duties but laptops do not usually have the Power-On-AC option (or power-on-lan-activity). With power-on-ac Rooter turns On/Off just like any other appliance when one messes with the power cord. That's as wife-safe as a computer can get :)