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One String Miner Test 1

Today I was wondering why the first 8 build OSM (One String Miner) only hash between 23 en 26 GHs. I measured the voltage input in the boards: 11.4 V !! The PCI-E connectors from the PSU “only” supply 11.4V instead of 12V. Weird, I will investigate tomorrow. I had 4 DIY-1 kits left, build the first one just standard: pcb + heatsink. For power I used a cheap 12V 10A PSU from Dealextreme. You can adjust the 12V power output on the PSU some time for some tests:

No thermal paste between PCB and Heatsink + Artic F8 Fan (very low RPM)

Voltage [V] Temp [°C] Hashrate [GH/s]
12,22 56 32,8
12,30 58 32,26
12,14 57 32
11,91 54,6 31
12,40 59 31,6
12,10 56 31,4

With thermal paste between PCB and Heatsink + No Fan We will see how temperate gets higher after x seconds

Voltage [V] Temp [°C] Hashrate [GH/s] Time [sec]
12,10 35 31,70 10
12,10 36,6 31,80 60
12,10 39,2 32,05 120
12,10 40 32,08 180
12,10 40,7 32,14 240

With thermal paste between PCB and Heatsink + With Fan (other than the Artic) We will see how temperate gets drops after x seconds. I connected a fan “on the fly” and started measuring form 40,7 °C to ….

Voltage [V] Temp [°C] Hashrate [GH/s] Time [sec]
12,10 40,7 32,14 0
12,10 35 32,06 20
12,10 32,8 32,04 180
12,10 32 32,04 240

Conclusion: use thermal paste (non conductive), it could reduce temp more than 10°C. As an extra test I recuded power input to the board to 11,5V and the hashrate dropped to 26 to 29 GHs. So the Voltage input should be at least 12V for 30+ GHs hashrate. What you also see is you will loose some power thru the cables. 12.10V on the PSU = 12.02V on the PCB. On the photos you will see also the other 8 boards connected to the PC-PSU in cgminer (0,2,3,4,5,6,7,8,9).

All boards are build now…

Movie (not hashing at optimal hashpower yet)

Update 00:26h: Be Quiet Pure Power 600W PSU sucks, it only provides 11,5V from the PCI-E and other 12V connectors. Took a Seasonic S12G and this PSU provides 12.1V (max), better  Grin de 4 DIY1 boards with the cheapo dealextreme 12V 10A PSU is turned up to 12.6V. Now 12 boards are hashing at a total of ± 400GH/s (± 33GH/s per board). Next few days more tuning and testing. cgminer 12 OSM @ ±400GH/s

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  1. nice review, and how many bitcoins are generating at this moment?
    How much electricity are you using? I’m also interested in one of these boards

    • I have 12 OSM boards running, 8 on stock 12V, 4 on 13.1V

      Eligius Pool : Estimated Earnings
      Your approximate maximum potential earnings at the current network difficulty of 6,978,842,649.59 and maintaining your 3-hour average hash rate of 382.33 Gh/s is 0.02755162 BTC per day.

      These are great boards, low power consumption and almost no noise (I use 3 simple 12x12cm Fans). I have some for sale so if you are interested send me a message.

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