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I don't really understand this totally. Any GPU I plug in for mining other than the one attached to the primary monitor will remain unavailable for mining in windows? If this is so, does cycling the monitor through the GPUs activate them for mining? These steps would work?

1. Install 3 GPUS

2. Start mining on 1st GPU.

3. Switch monitor to 2nd GPU, start mining.

4. Switch monitor to 3rd GPU, start mining.

This would allow me to run all 3 GPUs without a dummy plug in 2 of them, right?

For Windows, yes, but every time something hiccups you have to do it all again. Just sticking a single resistor into the HDMI socket does make it a lot easier.

Would sticking a DVI cable to the monitor in the 2nd GPU, and sticking an HDMI cable to the same monitor in the 3rd GPU work the same?

I'm mining with on Windows my two 5850's and didn't ever thought about need to use the dummy plugs, it isn't needed!
You just need to disable ULPS - this mechanism disables the second card without monitor/workload. Here's how to do it:

Yes it would, and I have done that in the past.

I now use a KVM.

If you happen to have enough monitors in your place, you could temporarily attach them to the GPUs prior to start up. Once you are in windows, you can then remove all the monitors you don't want to use on that system and put them back where they came from (wife's PC, Kid's PC, etc). Now windows will see all your GUPs even though they have nothing plugged into them :)

KVM ftw... 1 monitor, 1 keyboard, 6 GPUs :)

I had the same issue but didn't need to do anything in hardware, only software. Not sure if this applies to your setup but it did work for mine (2x5770s) so you may have some luck. I went into the monitor configuration (screen resolution in Windows 7) and enabled my desktop to extend to the display showing from the second card. Nothing is plugged into the card but it did enable it, I set it to 800x600 and moved it to the upper right corner so I don't move into it by accident often.

Awesome, you are the man !

Noted, just in case of future development :)

Cool very useful. So I can do this, restart windows, and I can mine with all the GPUs?

Can anyone confirm that this works?

Not working at all for me.

If the registry hack works it would mean I just bought 4 dummy plugs for nothing :P

Anyone tried it on Win 7 64 bit?

Sir, you're a gentleman and a scholar.  I'll try that later.  Although I spent $16 and ordered 20 vga/dvi dongles and 100 capacitors to make the ghetto rigged dummy plug.

Not that I don't love having hdmi-hdmi for my main system, hdmi-dvi for gpu1 on miner and vga-vga/hdmi dongle - hdmi for gpu2 on miner :)

Awesome, I just ordered some new parts and forgot about the whole dummy plug thing, if this eliminates the need for them I won't have to bother.

I've had EnableUlps set to 0 for quite some time (Crossfire related problem with 1 card randomly going to 0% load).  I can confirm that this will NOT allow you to start mining on a GPU that doesn't have a monitor attached.

My solution.  My monitor has 3 inputs.  I plug my 2 cards in to it.  1 DVI 1 DVI-VGA.  Start mining and overclock 1st card, hit switch input, start mining and overclock 2nd card.

Just build a dummy plug, all you need are some resistors and a dvi/vga adapter/port.
I used to do this, but everytime my PC would restart or power went out, it was a bitch doing this every day!

Dummy plugs, no worries!

My linux server has 186days uptime.  Where do you live that power goes out that frequently?

Cheaper and simpler dummy plug.

http://www.overclock.net/folding-home-guides-tutorials/384733-30-second-dummy-plug.html

Its not about where I live lol..its my damn apartment circuit at home...1.2 ghash takes alot of power with these damn 5830s..i plug a hair dryer in and blows the circuit..

Umm that's nuts. You may want to put the miners on a separate circuit if possible. If for some odd reason you're running everything in the apartment off of a single circuit then whoever wired that apartment should be shot.

Did you set it up on all cards eg. under the 0000 and 0001 or 0003 keys? It works fine for me, my config:
Windows 7 x86
HIS Radeon 5850
ASUS Radeon 5850 DirectCu TOP
Latest catalyst drivers.
CrossFireX enabled
Cards are linked with CrossfireX bridge. If it still doesn't work, there's another solution, run furmark or another GPU heavy application for a minute, then the second GPU will appear ready for mining - I was doing this before learning the ULPS trick.

This did not work for me either. I had changed all 3 keys to 0, but my cards are not linked by a CrossfireX bridge. I expect the CrossfireX bridge is the key here. If so, then I will stick with a KVM, as crossfire has a detrimental affect on the mining performance.

I tried this registry tweak too under Windows 7 32-bit without crossfire on keys 0000 0001 0002 and 0003.

Didn't work.

I do something similar but not really.

I'm using Pheonix as my RPC miner, and I do this

Step 1: Start miner on Card 1
  phoenix.exe DEVICE=1
Step 2: Switch VGA/DVI/HDMI cable to Card 2
  Phoenix.exe DEVICE=1
Step 3: Switch VGA/DVI/HDMI cable to Card 3
  Phoenix.exe DEVICE=1

Notice the device number is the same, but it initiates the process thread depending on the Active GPU in windows.

I have only tested this in Windows 7, no other operating system.

Works for me :)

Hope this helps.

Some more confirmations from somebody else? Looks like good and easy method.

I would (personally) avoid this - if the wires cross somehow you're blowing the vid interface rather than your VGA converter.  Use the VGA converter that comes with every video card, and just put the resistor between pins 1 and 6 - you only need one resistor (there is no benefit to 3, just costs 3x as much).

W

If that is the case I highly recommend you plug into a different outlet as well as get a battery backup.

I got a battery backup and put mine in the basement where it has a 20Amp breaker and the only other thing hooked up is a freezer.

If you are blowing the circuit breakers all the time I would be worried.

you the man.

I dont get how you people get 2 cards running at all without the crossfire cable. I have 5 machines, each with 2 5970's in them. If I try to run them with a dummy plug and without the crossfire cable, they will run for a few minutes then the system will crash and it'll say there was a "Hyper Transport sync flood error" and I have to reinstall the drivers before all 4 cores are recognized again.

I use a KVM and 1 monitor.

Monitor goes into KVM

cables go from KVM into GFX cards of my computers

job done :)

if I use linux, I don't need dummy plugs right? just planning hardware right now

Correct.  All mine are headless even.

Confirmed. Solved all my issues. Also the hash rates are more stable and less heat: Winning!

OK, I would like to sum up what we know about dummy plugs. It has been bothering me quite a bit. Please correct and extend.

• Linux: no dummy plugs needed
• Win7: it is possible to force activate screens in display properties or change the EnableULPS registry entry
• WinVista: ?
• WinXP: dummy plugs or crossfire needed? did anyone manage to get it to work some other way?

Ive got Vista Ultimate running 2x cards, NOT in crossfire, 1 with a monitor hooked to it, and 1 with a dummy plug.

Ive also got Windows XP running 4x 5850s using dummy plugs, no crossfire cables.

a signal from resistor can blow the vid interface or the VGA converter? how does that work exactly?

A standard HDMI port outputs digital in the block connector and standard analogue VGA on the cross connector. All a HDMI to VGA plug does in put the analogue connectors to a VGA pin format.

Analogue VGA outputs a Red, Green and Blue signal, known as RGB. All you need to do is put a resistive shunt across one channel to make Windows think you have a monitor attached.

Putting a resistor across the R, G or B channel (or all 3 if you mistakenly think it will make a difference) has the same affect whether you use the HDMI analogue connectors or the VGA adaptor analogue connectors. If you cross the pins on the HDMI to VGA adaptor it will have EXACTLY THE SAME AFFECT as if you'd crossed them on the HDMI connector.

The only difference using an adaptor has is that it may cost you more money.

I'm really surprised nobody has mentioned the benefit to NOT using dummy plugs.

I use the swap-monitor trick to get them all going because, for example, my 5830 does 300 MH/s with the monitor plugged in.  When I unplug the monitor to swap over to the 5850, the hashrate goes up to 304 MH/s.

I'm assuming dummy plugs would decrease all hashrates by 1%

how did you measure the 1%?

That's 100% false and not working. ULPS is the powersaving feature on cards that are already in CrossfireX therefor active.

I guess I should have just stated the overall hash rate increase,

350 -> 356

300 -> 304

obviously the increase is because the gpu no longer has to render the desktop

I did a measurement on the influence of the dummy plugs on hashrate. Result: No significant influence (-0.7% with plugs removed).

Measurement: 3 5850 cards. Two miners on each card summed up. Two measurements before removal of plugs, two measurements after. Phoenix with flag -a 128 for measurement averaging. Waiting time between measurements ~2 min.

I am quite reliefed that with this result I do not have to look for a way to make the cards work without dummy plugs on win xp.

I'm running WinXP x64 and 2x 6970's

I have tried dummy plugs, but can't get the second card to go active.

This is what I tried:
http://www.overclock.net/folding-home-guides-tutorials/384733-30-second-dummy-plug.html

Even tried this:
http://blog.zorinaq.com/?e=11

No luck on either, any ideas on what else I can try?

EDIT:
Figured it out, you have to extend your desktop on the other card.

Here's what I did

I have 2 7970 and a onboard video card.

At first I was using one of my 7970 HDMI to mine/browse on my computer, but I did notice it effect my harsh rate a bit (jumpy at 620kh/s - 580kh/s ish when I load stuff). So I was thinking maybe I should use my onboard video card to display instead, but when I switch the hdmi cable to my onboard, system wasn't detecting the 2 7970.

So I found a way to mine with my 2 7970 without effecting my harshrate and continue to browse on the internet with stable harshrate and without using a dummy plugs either.

1 HDMI from onboard to monitor, 1 DVI to vga from 1 7970 to the same monitor.

Set onboard screen as main, and 7970 as extend. Done (You can't just use 1 montior or it won't detect the 7970.)

Harshrate is stable at 620kh/s even when I load 5 tabs on chrome.


I am not sure if my 7970 will harsh even higher if it didn't have to render the extended screen. Might switch the DVI cable to my other 7970 to find that out.

Update: (It does not effect the harshrate unless you have something on that screen.)

You didn't notice this was a 2 year old thread, right?

Well if I did I wouldn't post now right? :P