J.D. Hodges

You’ve probably read some sensational news stories about Bitcoin mining, I know I have . 🙂 However, I had lunch with a buddy last month in Tulsa and it really altered my view on Bitcoin mining. I already had an abstract idea about random people out there using CPU/GPU computing power to generate blocks to continue the growth of Bitcoins, what I didn’t realize was that my buddy knew a guy that was sinking big bucks into a personal Bitcoin farm…

Note: more info on the basics of what Bitcoin mining is:

https://en.bitcoin.it/wiki/Category:Mining

This lunch occurred on my last trip to Tulsa to install a new server at the datacenter. My favorite techie there usually takes me out to lunch. This time he told me about a friend and (potential client of the datacenter) that had a 30 system bitmining operation going on and that had apparently been making a lot of cash money with it.

The friend needed more power to feed his machines, which is no surprise considering the power hungry video cards that are best at Bitcoin mining. As most people involved in server farms or datacenters will tell you, power usage (and having a reliable power source) is a very important issue! We didn’t know how the recent Bitcoin crash had affected the local mining operations but it definitely piqued out interest.

Since that lunch I have been meaning to learn a bit more about Bitcoins. Here are some preliminary links that I hope will help you too if you are interested in the topic. I will also try to find out more about the friend that invested so heavily in Bitcoin mining!

#1 My favorite Bitcoin site so far: a bitcoin blog that is fun and informative 🙂

Here’s the link to a fun blog with cool Bitcoin posts and examples of real world systems and their performance (benchmarks) as well as plenty of examples of the energy used and heat generated by these systems:

 

 

#2 GPUs are best for Bitcoin mining

And AMD video cards (GPUs) are the BEST hardware for mining bitcoins, better than CPUs, better than NVIDIA… and here an explanation as to why:

https://en.bitcoin.it/wiki/Why_a_GPU_mines_faster_than_a_CPU#Why_are_AMD_GPUs_faster_than_Nvidia_GPUs.3F

I was a bit sad after finding this out, as I have a number of relatively high-end systems and servers with fast multi-core CPUs. Alas, most of my video cards are not the highest end parts and a lot of them are NVIDIA  🙁 So, very little likelihood of me putting spare resources to use…

Quoted from the bitcoin.it wiki:

Why are AMD GPUs faster than Nvidia GPUs?

Firstly, AMD designs GPUs with many simple ALUs/shaders (VLIW design) that run at a relatively low frequency clock (typically 1120-3200 ALUs at 625-900 MHz), whereas Nvidia’s microarchitecture consists of fewer more complex ALUs and tries to compensate with a higher shader clock (typically 448-1024 ALUs at 1150-1544 MHz). Because of this VLIW vs. non-VLIW difference, Nvidia uses up more square millimeters of die space per ALU, hence can pack fewer of them per chip, and they hit the frequency wall sooner than AMD which prevents them from increasing the clock high enough to match or surpass AMD’s performance. This translates to a raw ALU performance advantage for AMD:

• AMD Radeon HD 6990: 3072 ALUs x 830 MHz = 2550 billion 32-bit instruction per second
• Nvidia GTX 590: 1024 ALUs x 1214 MHz = 1243 billion 32-bit instruction per second

This approximate 2x-3x performance difference exists across the entire range of AMD and Nvidia GPUs. It is very visible in all ALU-bound GPGPU workloads such as Bitcoin, password bruteforcers, etc.

Secondly, another difference favoring Bitcoin mining on AMD GPUs instead of Nvidia’s is that the mining algorithm is based on SHA-256, which makes heavy use of the 32-bit integer right rotate operation. This operation can be implemented as a single hardware instruction on AMD GPUs (BIT_ALIGN_INT), but requires three separate hardware instructions to be emulated on Nvidia GPUs (2 shifts + 1 add). This alone gives AMD another 1.7x performance advantage (~1900 instructions instead of ~3250 to execute the SHA-256 compression function).

Combined together, these 2 factors make AMD GPUs overall 3x-5x faster when mining Bitcoins.

[end quote] Original source:
https://en.bitcoin.it/wiki/Why_a_GPU_mines_faster_than_a_CPU#Why_are_AMD_GPUs_faster_than_Nvidia_GPUs.3F

This also explains why high-performance cards like the AMd 5970 are especially hard to come by! (see the nice table below)

Single Card Setups

Model	Price	Availability	Avg. Mhash/s	Mhash/J	Mhash/$
5770	$136	Moderate	212.83	1.45	1.56
5830	$140	Moderate	286.45	1.4	2.05
5850	$250	Limited	325.49	1.73	1.3
5870	$350	Limited	393.46	1.9	1.12
5970	$730	V. Limited	655.83	2.01	0.90
6750	$116	Easy	167.59		1.44
6770	$115	Easy	196.67		1.44
6850	$160	Easy	213.7	1.35	1.34
6870	$190	Easy	278.31	1.73	1.46
6950	$250	Easy	360.62	1.8	1.44
6970	$350	Easy	389.55	1.72	1.11
6990	$770	Limited	758.82	1.91	0.99

Source: https://en.bitcoin.it/wiki/Mining_hardware_comparison#Single_Card_Setups

These quotes from the bitcoin.it wiki were released under a CC attribution license which Ihave attempted to comply with…

Additional GPU performance data:

More to come…

I will try to keep updating this page as I learn more about Bitcoins.