On mining profitability

With the price of litecoin and bitcoin on the rise, I’ve received a tremendous amount of email over the past couple weeks from people wanting to know whether or not it’s “too late” to get into mining. Or how soon one can expect to break even on a new mining rig purchase. Or what my predictions are for the future value of cryptocurrency in general. I’ve responded to many of you already, but it probably makes more sense to post something here publicly.

Full disclosure: I don’t have a crystal ball. I have no idea what the future holds with regard to bitcoin or litecoin valuation. There are far to many variables and unanswered questions—especially on the regulation front—to make predictions with a high degree of confidence. However, I’d be happy to share some observations that I’ve made over the past few years, and offer my 2 cents in a general sense. Read on if you’re interested.

PSA: Don’t use GPUs to mine Bitcoin!

USB ASIC miner

A couple of these ~$20 USB ASIC miners are just as effective as a $300 GPU when it comes to SHA-256 (Bitcoin) mining.

With the recent price surge of Bitcoin, I’ve been getting a few messages from people asking about the viability of building a GPU-based rig to mine bitcoins directly. Don’t do that! GPU mining is only suitable for scrypt-based cryptocurrency (Litecoin, etc).

If you’re interested in mining Bitcoin, then you absolutely must use ASIC hardware if you hope to turn a profit. For example, six of these will mine as many bitcoins as a full-size triple GPU rig, and they’ll do it at less than 10% of the cost and power consumption (remember to pick up a USB hub if you plan to run a few, and perhaps a small fan or two—they run fairly hot)!

The downside to ASIC-based mining is that the hardware cannot be re-purposed once it becomes obsolete—and with the rapidly-increasing Bitcoin mining difficulty, that will happen fairly quickly unless the price of the currency keeps pace. Remember that you can always mine scrypt-based coins with your GPUs and trade them for bitcoins on an exchange, as well.

Undervolting in Linux via modified video BIOS


Before VBE7: Creating custom vBIOS files meant manually editing hex and hoping for the best—yuck!

For a long time, I’ve held off on writing a guide about modifying your video BIOS for the purpose of lowering voltage. Undervolting has the potential to reduce power draw by about 50 watts per GPU, so it’s easy to understand the appeal—you’ll see a significant savings on your electricity bill if you’re running a 3×7950 rig (like the one in my guide) 24/7. Unfortunately, the AMD Radeon drivers in linux don’t allow voltage control, so the only current way to lower voltage below manufacturer-specified levels in linux is to modify your video card’s BIOS.

In the past, such a hack involved manually editing your vBIOS file by hand, using a hex editor. Most folks hesitate to make such a modification, as performing the edit can be tricky if you’re not familiar with hexadecimal—and a mistake can mean a bricked GPU. Due to the potential danger I had decided not to post a guide about manually modifying your vBIOS ROMs. After all, nobody wants to be left with a $300 paperweight after inadvertently trashing their video card.

Enter VBE7, a GUI-based vBIOS editor for Radeon 7xxx series GPUs. Now anyone can easily make changes to their vBIOS without having to muddle around in a hex editor, praying they get things right. I’ve been testing VBE7 for a few days now, and it appears to work brilliantly. Read on for my guide on creating your own custom power-saving vBIOS!

bitcointalk.org forums hacked, user accounts for sale

The popular cryptocurrency forum bitcointalk.org (the site is currently down) was breached by hackers yesterday. Apparently the hackers were able to gain access to the site database and obtain the complete list of ~150,000 user accounts, along with each user’s hashed password. The hackers are now offering the list up for sale to any interested buyer for 25 BTC. There is some more information in this reddit thread.

If you had an account on the bitcointalk forums, make sure that you’re not using the same login/password combination anywhere else. While the user passwords were hashed, they’ll likely be cracked at some point.

Here is a copy of the email that I (and presumably every other bitcointalk forum user) received from the bitcointalk admins earlier today:

Unfortunately, it was recently discovered that the Bitcoin Forum’s server
was compromised. It is currently believed that the attacker(s) *could* have
accessed the database, but at this time it is unknown whether they actually did
so. If they accessed the database, they would have had access to all
personal messages, emails, and password hashes. To be safe, it is
recommended that all Bitcoin Forum users consider any password used
on the Bitcoin Forum in 2013 to be insecure: if you used this
password on a different site, change it. When the Bitcoin Forum
returns, change your password.


Passwords on the Bitcoin Forum are hashed with 7500 rounds of
sha256crypt. This is very strong. It may take years for
reasonably-strong passwords to be cracked. Even so, it is best to
assume that the attacker will be able to crack your passwords.
The Bitcoin Forum will return within the next several days after a
full investigation has been conducted and we are sure that this
problem cannot recur.


Check http://www.reddit.com/r/Bitcoin/ and #bitcoin on Freenode for
more info as it develops.


We apologize for the inconvenience.

mcxNOW paying out interest on cryptocurrency deposits

Yesterday, mcxNOW—a cryptocurrency exchange supporting Bitcoin, Litecoin, and several other altcoins—started paying its users interest on their digital deposits. The interest rate is variable and dictated by the trading fees collected by the exchange.

It’s an interesting move, and if it’s successful in significantly growing mcxNOW’s user base, you can bet that other exchanges will launch similar programs. Remember that while earning interest on your deposits may feel very bank-like, you’d be wise to treat online exchanges as your own personal cryptocurrency piggy banks at your own risk.

Bitcoin kiosks coming to five Canadian cities

Soon, Canadians will be able to exchange cash for Bitcoins at automated kiosks similar to ATMs. Bitcoiniacs, a Vancouver-based brick-and-mortar bitcoin broker, has ordered five of the kiosks and intends to roll them out across Canada in the coming months. The first machine is expected to land in Vancouver this October.

From the article:

The kiosks allow users to select how much money they would like to spend, insert cash into the machine and then scan a QR code on their phone to transfer the Bitcoins to their wallet. It also allows users to redeem their Bitcoins for cash.

1000 watt gold-rated modular power supply for $125 after rebate at Amazon

Amazon currently has an excellent deal on a Cooler Master 1000 watt gold-certified fully modular power supply. It’s $125 after a $30 mail-in rebate, which makes it about $75 cheaper than its normal price (new units on eBay typically sell for nearly $200). This PSU is reportedly a re-badged Seasonic and should have no problem providing efficient power to a rig with four undervolted 7950 GPUs (or three full-voltage cards).

Update: Looks like the deal has ended. The rebate is still available, but Amazon has raised the price back to its normal level. Hopefully some of you were able to snag one!

Update: The deal is still valid, although it looks like it’s been pretty popular, with shipping estimates in the 1-2 month range.

Android Bitcoin & Litecoin wallets potentially vulnerable to theft due to coding flaw

Due to a serious flaw in the Java secure random number generator used by many Bitcoin applications on the Android operating system, any wallets generated by Android apps are potentially vulnerable to theft. While the advisory on bitcoin.org only mentions Bitcoin, the flawed code is also used in many Android Litecoin wallets, and probably also in whatever wallets exist for the various other cryptocurrencies.

If you have an Android wallet application on your mobile device, I highly recommend that you immediately generate a new address with the appropriate official desktop client (click here for Bitcoin and and here for Litecoin) and send all of your coins there. Do not use a cryptocurrency wallet on the Android OS until you can confirm that the version you’re using has been patched to fix the vulnerability, and discard any previously-generated wallet addresses permanently.

Update 8/12: The BBC has posted an article on the issue.

Update 8/14: And the first confirmed thefts due to the bug are starting to be reported.

Sapphire 7970 GPU $299 after rebate at Amazon

Amazon is currently selling Sapphire 7970 video cards for about the same price as a 7950—$299 after a $20 rebate. While I generally don’t recommend Radeon 7970 GPUs as my top choice for mining due to their higher power consumption and up-front cost compared to the 7950, if you have abnormally cheap electricity or plan to also use your GPUs for other purposes (e.g.: gaming), then this is good deal.

CyberPower 900W Intelligent UPS deal at Amazon

If any of you are looking for a quality UPS & surge protector for your mining rigs, Amazon currently has a deal on a 900 watt CyberPower unit. 900 watts is plenty for a three GPU rig and will give you enough time to cleanly shut down your rig in the event of an outage (the unit is capable of performing the shutdown automatically in both Windows and Linux).

$115 with free shipping (or $95 if you have an Amazon Visa card & use promo code JUL20PER) is pretty much the lowest I’ve seen a 900 watt UPS from a reputable brand, so if you’re in the market this is a good opportunity to grab one!