How to create dummy plugs for your graphics cards

How to create dummy plugs for your graphics cards


With the popularity of crypto-currency growing due to the recent price hike, many joined in  to mine the digital currency. If you are not familiar with crypto-currency yet, it is a decentralised digital peer-to-peer currency that runs on the network of users that employ it. Cryptography is used to secure transactions. The process of adding transaction records to the public ledger of past transactions is known as mining as the users are rewarded with coins for the effort. However, the difficulty is increased each time a new block is created, as a result more sophisticated mining rigs are employed for the purpose of mining these digital currencies.


Bitcoin is the first crypto-currency introduced. Litecoin being its younger sibling is based off the concept of the ever growing Bitcoin and uses a scrypt based algorithm, unlike Bitcoin’s SHA-256.The scrypt algorithm is more reliant on memory, not processing efficiency. That is the reason those specialized hardwares developed for Bitcoin mining will not work with Litecoin and making GPU mining more effective.


If you want to run a GPU miner like CGMiner or BFGMiner with more than one graphics card connected, and if you are using any version of Windows, you will need a monitor attached to each graphics card, or use a dummy plug to make it seem so. You need to tell Windows to spread the picture over all your graphics cards. Windows XP will happily assume each graphics card has a monitor attached and try to spread the picture over a monitor which you do not have. Windows Vista checks to make sure.
In this turorial, we will look at how to make a dummy plug using three resistors and either a 15-pin D-plug or a DVI-I to VGA adapter, which is included with most graphics cards. You can solder the resistors to the 15-pin D-plug, or simply stick them in the holes of the DVI-I to VGA adapter.


How to create VGA dummy plugs

Dummy plugs are used to trick the computer to think there are additional monitors being detected on a MultiGPU folding solution. The GPU clients will not let you fold unless it detects a monitor. and if you dont have multiple monitors, you will need dummy plugs to make it think it does.

Step 1 : What will you need

  • DVI to VGA adapter
  • 75 Ohm resistors x 3 (you can also use 68 Ohm or 82 Ohm resistors)
  • A clipper to cut the ends off the resistors to make them even


Step 2 : Prepare the resistors

  • Bend one leg of the resistor till it is parallel to the other.
  • Clip off the longer leg so both legs are of same length.
  • Repeat on all 3 resistors.


Step 3 : Secure the resistors on to the VGA adapter

The diagram below will give you a better idea of where the resistors should go.


You need to bridge the top three pins on the right with the pins directly below it one-to-one. So hold the plug in a way that the wide part is up top.


Alternate the resistors so the leg of one is against the body of another to avoid shorting out the jumpers.


That’s it. Plug the dummy plug on to your GPU to trick your OS that there is a monitor attached to it and prevent the hardware from being idled.


How does it work

The graphics card sends separate picture information on three separate channels, red, green, and blue. Each of the three channels has a pair of pins

  • pin 1 is Red Signal
  • pin 2 is Green Signal
  • pin 3 is Blue Signal
  • pin 6 is Red Ground
  • pin 7 is Green Ground
  • pin 8 is Blue Ground

If there is a monitor attached, it takes a few milliamps of current from the graphics card. The computer tests whether a current is flowing from the Green Signal on pin 2. If there is, it is assumed that an old-fashioned VGA or SVGA monitor is connected. The resistor connecting pins 2 and 7 causes the same amount of current to flow as a monitor would.


What Ohm resistor can i use

Anything between 50 and 100 ohms will probably work. If you use less than 50, you will be drawing too much current, perhaps. If you use too high a value, perhaps not enough current will flow to simulate a monitor being connected. In the UK, Maplin M75R metal oxide resistors are the easiest to buy, but the wire is a bit thin to stick in the holes of a DVI-I to VGA adapter. It is said that 1/2 watt carbon resistors have thicker wire that is just the right size. In the USA, 75 ohm resistors are harder to find. You can use 68 ohms or 82 ohms instead.

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