When Litecoin was originally created, it was supposedly “GPU-resistant”: the Scrypt algorithm chosen and implemented would mean only CPU mining would be viable, keeping the network evenly distributed.
However it wasn’t long before folks had worked out how to tweak their GPU setups to allow them to run the Scrypt algorithm far more efficiently than a CPU. Some event claim that the creators of Litecoin knew this and mined the coin with GPUs from its inception. Either way, the viability of CPU mining for Scrypt started to take a serious dive in 2013.
“But Litecoin and Scrypt algorithms are still ASIC-resistant”, almost everyone claimed. The implementation required far too much high-speed memory to make it possible. Then, whispers on forums and websites started up in Q3 2013, talking about working Scrypt FPGAs and ASICs that were being developed overseas. And starting in January 2014 the devices began to materialize.
The day is upon us folks. Scrypt ASICs are in the wild with next generation hardware already taking pre-orders. The first round of Scrypt ASICs come in two form-factors:
- The 1-chip USB thumbstick sold and branded by DualMiner
- The 5-chip Orb design sold by numerous resellers (without any noteable branding)
Both of these devices are powered by the GC3355 ASIC from GridSeed. This chip can hash both Scrypt and SHA and is even capable of doing both at the same time (hence the DualMiner name). The DualMiner U1 has a single GridSeed GC3355 chip clearly visible on the back-side of the device. It also features a physical dip-switch for toggling the device between 0.9V and 1.2V.
Unfortunately both the 1-chip and 5-chip devices came to market with their own custom software, meaning you could not mine with either the DualMiner or Orb miners with CGMiner or BFGMiner. You had to use either the reseller’s binaries or compile their custom software yourself, if the source was available.
The good news is that I have been actively working with several vendors of GridSeed hardware for the past couple of months on native support for both the 1-chip and 5-chip GridSeed ASICs in BFGMiner. CGMiner no longer supports any algorithm or coin other than SHA-2 and Bitcoin, so BFGMiner was the natural choice. And as of yesterday the DualMiner driver has been merged into BFGMiner so I can finally provide a proper walkthrough on OS X!
As with many of the previous ASICs, DualMiner is currently only supported by BFGMiner. So, the first step is to install BFGMiner on OS X. There is a thread here on the Bitcoin Talk forums which discusses various ways to install bfgminer on Mac OS X. The most full-proof method is to use Homebrew:
- Launch Terminal.app from Spotlight or your Applications folder
- Install Homebrew by entering the following in the command prompt:
ruby -e "$(curl -fsSL https://raw.github.com/mxcl/homebrew/go/install)"
- Run the following command and then fix any reported issues:
- Tap the following Homebrew repository so that you can install packages from it:
brew tap nwoolls/xgminer
- Finally, install bfgminer:
brew install bfgminer
The setup here similar to BFL devices. Before mining you will need to install the Virtual COM Port Drivers from FTDI found here.
Because OS X has its own FTDI driver, under some circumstances you may need to manually unload that driver and load the official FTDI driver:
sudo kextload -b com.apple.driver.AppleUSBFTDI
sudo kextunload -b com.FTDI.driver.FTDIUSBSerialDriver
With the BFGMiner properly installed and the USB to UART driver installed, you can use the -d? argument to list available devices with bfgminer:
bfgminer -d? -S noauto -S dualminer:all --scrypt
[2014-03-21 19:08:16] Started bfgminer 3.99.0
[2014-03-21 19:08:17] Devices detected:
[2014-03-21 19:08:17] Device (driver=dualminer; procs=1; path=/dev/cu.usbserial-000050FDA)
1 devices listed
Note the additional
--scrypt argument since we will be Scrypt mining. I’ve also included the
-S noauto argument to prevent GPU detection (for simplicity).
Once the DualMiner U1 is detected you can start BFGMiner using the -o, -u and -p arguments to begin mining:
bfgminer -S noauto -S dualminer:all --scrypt -o hostname -u username -p password
You can also over-clock the DualMiner U1 using BFGMiner and the
--set-device argument. Currently the following rates are supported: 400, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1100, and 1200 (850Mhz is the default).
bfgminer -S noauto -S dualminer:all --set-device dualminer:clock=850 --scrypt -o hostname -u username -p password
The GridSeed chips also support Dual Mode mining: mining both SHA-2 and Scrypt at the same time. Note that with the DualMiner 1-chip device you should change the hardware dip-switch from L to B to lower the voltage. Doing this requires running two instances of the miner (BFGMiner in this case), one of them with an extra argument.
First, launch the SHA-2 miner instance:
bfgminer -S noauto -S dualminer:all -o hostname -u username -p password
Then launch the Scrypt miner instance with the
bfgminer -S noauto -S dualminer:all --set-device dualminer:dual_mode=1 --scrypt -o hostname -u username -p password
Note that, as seen above, running in Dual Mode will result in a slower Scrypt hashrate: approximately 30Kh/s rather than 70Kh/s.
If you have any questions feel free to post them in the comments below or on this thread at the Bitcoin Talk forums. And now, happy Scrypt ASIC mining!