Our seismograph network is held together by DMP eBox 2300 computers. These things have 200 MHz 486DX compatible CPUs, 128 MB RAM, and a CompactFlash slot that we populate with a 4 GB SLC NAND card (that are now ridiculously hard to find). The computers come in a nice, small, passively cooled metal case, cost about $150 each, and draw a few watts at idle.
Now, sure, we could get ARM-based systems that are cheaper, faster, and even less power hungry (and I hope in the future I can start using such systems!), but for now, I'm stuck with x86 because we have to run a proprietary Linux/x86 binary on each computer to get the data out of the digitizers and into a "common" data format.
(One day I'll write my own code to replace that proprietary binary, and then the company that makes a small, sub-$100 ARM board that boots Linux and has a flash memory slot of some sort, two Ethernet ports, and two real [not TTL-level] serial ports will be my most favorite company in the world.)