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.
20 thoughts on “How to create dummy plugs for your graphics cards”
great tutorial, saved me the hassle of buying pre-made plugs.
Will this also work if I just go from pin 5 – 10 without doing the others?
It has to be 1-6, 2-7, 3-8.
Thanks! It worked!
Glad to hear that our tutorial helped you.
I needed similar on my laptop. I found out the hard way by clipping and rejoining wires, so I can confirm it works. Indeed, I can confirm 150 ohm does not work, and that 40 ohm (lowest I dare go without risking my laptop) still worked. I also found out that only the green needed to be attenuated this way. Even with all the other lines open circuit, a modern Dell laptop (win7) thought there was a monitor attached and allowed me to set any resolution. I came here wanting to confirm this was not just a fluke and am thus grateful for the confirmation. Hope that is of interest.
I appreciate your comment.
This is useful but wanted to check is there a risk of fire? I’m not an electrician but sticking wires in sockets doesn’t seem like a good idea?
Hi, I was wondering if attaching a resistor is in any way way dangerous?
Maybe short circuits, fire, electric shock. Can anyone advise?
Milliamps flow. Not enough to make heat, no fire risk. 5 volts, no shock risk. You’re not connecting to mains for goodness sake, the computer uses 3.3 to 12 vbolts. You can’t get a shock off your car battery can you?
Not fire, or electric shock. A little smoke at the most if you manage to damage your graphics card.
5 volts aren’t dangerous, but they can demand as many amps as the card power generator is able to supply.
It just takes a short circuit for this to happen. If the card isn’t protected a funny burning smell could reach your pituitary when it’s too late.
I can confirm it works for 100 Ohm
Done and working fine with 100 Ohm resistors. Thank you for the great info!!
I done it with 100 Ohm resistors and it works, thanks! I guess if there’s a way to obtain more than 1024x768px of max screen resolution.
that’s possible to display 1080p(1920*1080)??
Works on DVI-D only digital?
How to know that the plug is working in windows? 🙁
I set this up but not sure if I did it right.. Either way my purpose didn’t resolve as well.. So how to test if this is working?
I mean EDID is better than that 🙂
Actually, card won’t work when you remote the computer, if you don’t it will work just fine even without any monitor or dummy plug attached. Amazing isn’t? You can check your nicehash status to see if it’s working
mine graphic driver another pc case in unavailable. how true graphic driver providing im? im not sure which whether?