Monthly Archives: October 2013

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

Hex

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.