With the majority of your cost in building a mining rig going towards your GPUs, consideration must be taken when deciding on the base of your rig.  There are two routes one can take when deciding on the base for their mining rigs which comes from deciding on your CPU, AMD or Intel.  AMD motherboards tend to run cheaper than the intel boards currently however the AMD Ryzen CPUs are running well over $200 in almost all cases.  For a budget rig, it currently makes the most sense to look at the Intel options first.

Most mining rigs today are built around the LGA 1151 CPU as most boards designed for mining rigs support this CPU.  We are going to take a look at both CPU sets to determine the absolute lowest cost base for your mining rig.  As more and more people get into mining, these components are becoming harder to find which is driving up costs.  The prices quoted are as of 15 Jan 2018.  If you can find them cheaper, then you will be coming about ahead of these calculations.

Looking at LGA 1151 CPUs you will find that the best three options are the Intel Pentium G4400 3.3 Ghz, Intel Celeron G3900 2.8 Ghz, and the Intel i3 6100.  There is also the option to attempt to find each of these in their lower wattage variants which is indicated by the “T” after the number.  The G4400T and G3930T are difficult to find new, but can be found on places like eBay if you want to buy one second hand.  I personally use a 6100T in one of my mining rigs as the core concept around that build was low power usage.  I also recommend the Kill-a-watt meter to see exactly how much your rig ends up pulling from the wall.  This device is very helpful in figuring out exactly how much your rigs end up costing to run.

Listed here, the best CPU for mining ethereum.
Go for the more cheaper versions,because for mining you don’t use CPU power.

$376,17
LGA 1151 DDR4 & DDR3L Support Display Resolution up to...
$114,00
Boxed Intel Pentium Processor G4400 (3M Cache, 3 Design that...
$109,00
Socket LGA 1151 Intel 200/1001 Series Chipset Compatibility (1. Excludes...