One of the nice things about Linux is that you can give use to your old computers. This weekend I put CrunchBang Linux (uses very low resources) on my old HP 6736 for mining with USB Erupters (not using any GPUs). It has a 667MHz Celeron, 256MB RAM, and USB 1.0 (http://h10025.www1.hp.com/ewfrf/wc/document?docname=bph06109&tmp_task=prodinfoCategory&cc=us&dlc=en&lc=en&product=60421). I'm pretty sure I couldn't have done that on Windows, and the cost was free. To save watts, I disconnected power to the CD and floppy drives and the setup uses only 42 watts when running, and would be even less if I had used a USB flash drive instead of the HD to host the OS. (For really low watts, you could go with a Raspberry Pi).
With everything running, including cgminer 3.1.1, I don't go over 135MB RAM and CPU use is negligible. The accepted shares, HW errors, and other measurements are in line with what I see in my other setups, so the age of the computer isn't affecting anything.
So, if you have Erupters and an old computer laying around, and you don't want to buy a RPi, put the old computer to use. Your only cost would be a powered hub (if using multiple Erupters).
Yes, you could have done this with Windows With everything running, including cgminer 3.1.1, I don't go over 135MB RAM and CPU use is negligible. The accepted shares, HW errors, and other measurements are in line with what I see in my other setups, so the age of the computer isn't affecting anything.
So, if you have Erupters and an old computer laying around, and you don't want to buy a RPi, put the old computer to use. Your only cost would be a powered hub (if using multiple Erupters).
That machine will be perfectly happy running any NT5.1 kernel based version of Windows, like Windows XP or Windows 2000.
By modern standards, that's going to be too slow for everyday work, but XP started out on such machines.
Erupters are only equipped with a USB->Serial converter (thats why they display as being on port COMx) and they will happily work under such conditions.
On the other hand, Linux is free, old hardware is usually free, so it is a great purchasefree option. It will draw far more power than an RPi tho.
But you could combat that by installing as little hardware as possible, using a USB Flashdrive or IDE->Memorycard adapter, installing as little add-in cards as possible (Linux will run without graphicscard and operated through Telnet or SSH, called "headless") and underclocking and undervolting the CPU.
If you do have some spare cash, an Intel Atom based board will also be a great idea. They will use around 10watt.