Quite recently, I wrote an article revealing the disadvantages to Bitcoin mining. More precisely, a major disadvantage to the actual Bitcoin mining process is the cost vs. revenue battle, where you may be spending more money on generating bitcoins than you are earning with the bitcoins you have mined. This can vary based on the hardware you use for mining as well as the current value of a bitcoin.
However, even if you have read about the disadvantages to the process and have read our Bitcoin guide, you may have still decided to go for it and build yourself one or more Bitcoin mining rigs. The CPU does not matter for any bitcoin mining machines as the GPU(s) will do all of the work. As this page explains, GPUs can do a lot more number-crunching than CPUs can, which leads to faster mining.
We also wrote another article which highlights differences between CPUs and GPUs without a focus on bitcoin mining. Therefore, even the cheapest AMD CPU will do just fine, as you will want to save the most amount of money. Choosing the best GPU, however, is a bit more difficult, so you will have to look at a number of different stats about them.
There are three different numbers about a GPU which will be of major interest to you, namely MHash/s, MHash/j, and MHash/s/$. Respectively, these are hashes per second, hashes per joule, and hashes per second per dollar spent on the GPU.
MHash/s describes to you the amount of number-crunching the device can do while bitcoin mining. If the number is higher, than the faster it will go through hashes. The more hashes you can process, the less time it will take before you come across a 50 Bitcoin chunk. With better hardware, your chances do not necessarily increase, but you will be able to go through more hashes in less time.
This can often be seen as a pure power statistic, although it does not indicate efficiency.
MHash/j describes the amount of hashes the GPU can process with 1 joule of energy. This is a good statistic for the amount of work it can do with a certain amount of electricity, so a higher number indicates that it is more efficient at number-crunching. If you plan to keep your mining operation running for a long time, then you will want to find a GPU with a really high number in this category.
Usually, the high upfront cost will be worth all the savings later on. Plus, if you are building many of these rigs, it will help prevent fuses from blowing.
Last but not least there is MHash/s/$. This is a good indicator of how well the GPU crunches numbers based on the cost of buying it — this does not include costs related to electricity for running the GPU (see MHash/j). A high number in this statistic means that dollar for dollar the GPU is better at crunching numbers.
If you choose a GPU that has a high number for both the MHash/j and MHash/s/$ statistics, then you will be running a very cost-effective card for what it is capable of doing. However, do not forget to at least look at the MHash/s statistic, because it can ultimately still be a very weak card.
You are never going to find the perfect card that boasts the highest values in all three statistics, but you can mix and match to find the card that seems best for you. If you are a fan of nVidia, then I’m sorry to say that you will need to go with an AMD GPU for your mining rig. nVidia cards do not have MHash/s values even close to as high as AMD cards. You can find these statistics on this page, which gets continually updated as new GPUs come out.
If you are still completely unsure about which would be a good card, may I recommend the AMD Radeon HD 5970 or AMD Radeon HD 5850? The 5970 has a very high MHash/s value as well as a decent MHash/j value, and the 5850 is decent at the MHash/j statistic and does fantastic with its MHash/s/$ value.
Do you have bitcoin mining rigs, or have you considered building one? Do you have any tips for aspiring miners? Any recommended graphics cards? Let us know in the comments!