The Mini Miner is designed as a low-cost, low-power scrypt mining rig. I built it because I already have several power hungry rigs running AMD cards and I wanted to try the new power-efficient Nvidia GeForce GTX 750 Ti cards. The result is a rig with a Kh/s per watt ratio that is much better than any of my other rigs. The dollar per Kh/s is not impressive, but I expected that with only two cards. Also, I was able to bring the cost per Kh/s down and Kh/s per watt up just by adding a pair of Gridseed miners running in scrypt mode to the Mini Miner. Update: I added two more Gridseed miners.
Major Components
| Motherboard | 760GM-P23 | $39.99 |
| Power Supply | EVGA 430W | $34.99 |
| CPU | Sempron 145 | $28.99 |
| RAM | (2) 1GB DDR3 1333 | $14.99 |
| GPU | (2) PNY GTX 750 Ti | $319.98 |
Power Supply: My search criteria was a quality brand, 80 Plus certified unit between 400 and 500 watts.
CPU: Go for the cheapest CPU the motherboard supports. Used is fine, just make certain it includes a heatsink.
RAM: Every GPU mining rig I own uses a total of 2GB of the cheapest used RAM I could find on eBay.
CPU: Go for the cheapest CPU the motherboard supports. Used is fine, just make certain it includes a heatsink.
RAM: Every GPU mining rig I own uses a total of 2GB of the cheapest used RAM I could find on eBay.
Accessories
| Case | Crate | $5.99 |
| PCIE Risers | (2) USB Style | $33.90 |
| Misc | 8Gb Flash Drive | $5.95 |
| Misc | Power Switch | $4.99 |
| Misc | Bumpers | $5.82 |
Risers: None needed for a single card rig, two needed for two cards.
Total
| 1 GPU | 2 GPUs | 2 GPU, 2 Gridseed | 2 GPU, 4 Gridseed | |
| Cost | $ 301.70 | $ 495.59 | $ 994.27 | $1400.47 |
| Kh/s | 256 | 512 | 1220 | 1950 |
| Watts | 112 | 186 | 204 | 222 |
| $ per Kh/s | $1.18 | $0.97 | $0.81 | $0.72 |
| Kh/s per Watt | 2.29 | 2.75 | 5.98 | 8.78 |
The Kh/s on the GPUs is based on default settings and I expect to bring it up an additional 20% after tuning, that will also improve the $ per Kh/s. The Kh/s on the Gridseed miners is based on a clock speed of 850MHz.
The Build
Gather your parts and tools and go ahead and put the CPU and RAM on the motherboard. To customize the plastic crate you can score it with a razor knife and break it with pliers. Or to speed things up you can use a reciprocating saw. You'll also need a handful of zip ties.
Here I cut out access to the ports on the motherboard. You'll only need a USB and the network port when it's all set up.
When running a single GPU it can be plugged directly into the motherboard. I had to cut out some of the crate to allow the GPU room to come forward enough to plug into the PCIE slot. I also had to cut out a small section of the bottom of the crate to clear space for the two prongs on the GPU bracket.
In the first picture I've positioned the bumpers to raise the motherboard off the crate. The second picture shows the motherboard in place and the 4 holes I drilled for mounting a PCIE extender. Some extender styles are narrow and don't have mounting holes, the ones I've chosen are the wider style with mounting holes.
Power supply mounted in the "case" with access to the switch and cable. I've since removed some additional plastic to allow more airflow through the power supply.
Here you can see I've secured the motherboard to the crate with zip ties, one towards each corner. I've also mounted the PCIE extender board with screws and attached cables.
When you put a GPU in the 16x slot on this motherboard it covers the 1x slot. That's fine for a single card system, but I want to run two cards, so the only option is to use two PCIE extenders. For GPU-0 I'm supporting the front of the card with the GPU bracket resting on the crate and secured with a zip tie. The back of the card is supported by the USB and power cables attached to the rear of the PCIE extender board and zip tied to the ATX power cable. On my other GPU rigs I support the back of the cards with a wooden dowel, but this video card is light enough to get away with supporting it by the cables.
Grab some more zip ties and secure the power supply and the loose power cables you aren't using. Then attach the power button to the correct pins on the motherboard and zip tie the button to the crate.
Nvidia cards are known to get an additional 15 Kh/s when plugged into a 16x slot. I will be replacing the riser for GPU-0 with a 16x to 16x unpowered version and see if it makes a difference.
Software
To run a Mini Miner with Debian Linux from a flash drive, follow the Installing Debian guide. You'll need a monitor attached to the card in the 16x slot and a USB keyboard. Leave the BIOS settings at default for now.
Unfortunately, this system locks at loading Nouveau drivers every time when booting a fresh install of Debian. Even trying to boot in recovery mode doesn't work. The workaround is to pull the PCIE risers off the motherboard and attach the monitor to the onboard GPU. The system will now boot. Perform the following steps to disable Nouveau:
Login as root with the password you created during installation
Create a new file:
Create a new file:
# nano /etc/modprobe.d/disable-nouveau.conf
Type or paste these three lines into the file:
# Disable nouveau blacklist nouveau options nouveau modeset=0To save and exit press: [CTRL]+[x] then [y] then [Enter]
Shutdown:
# shutdown now
Power off the system and reattach the PCIE risers and move the monitor cable back to the Nvidia card. Turn the system back on and hit [DEL] to enter the BIOS and make the following changes:
Change "Hold On" from [All Errors] to [No Error]
Change "Restore On AC Power Loss" from [Off] to [On]
Disable:
HD Audio Controller
PCI IDE Busmaster
On-Chip SATA Controller
COM Port 1
Change "Restore On AC Power Loss" from [Off] to [On]
Disable:
HD Audio Controller
PCI IDE Busmaster
On-Chip SATA Controller
COM Port 1
The system should boot successfully with the Nvidia cards now. If it does, you can unplug the monitor and keyboard and login with SSH from another computer. Follow the Nvidia Drivers and CudaMiner guide to get hashing.