dummy vga dongle

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(Test) Dummy VGA Dongle with Win7: Three Radeon HD 5770 and a Sin... http://www.geeks3d.com/20110622/vga-hack-test-dummy-vga-dongle-win...

1 of 18 7/7/2011 1:22 AM

Update: this VGA hack is mostly intended for Radeon graphics cards (see the comments section).

I recently played with multi-GPU and I needed to test one my GPU tools on three Radeon HD 5770 at the same time (noCrossFire). Under Windows 7, a graphics card is disabled by Windows if its not connected to a monitor. Not reallyconvenient if you need to test several graphics cards and if you have only one monitor.

If you look at the CCC (Catalyst Control Center), youll see the primary card (enabled) and two disabled cards:

Catalyst Control Center, primary card enabled


2 of 18 7/7/2011 1:22 AM

Catalyst Control Center, second and third cards disabled

Same thing with the GPU Caps Viewer OpenCL panel, only the first GPU (Juniper) is listed:


3 of 18 7/7/2011 1:22 AM

The second and third cards are disabled (for APIs like OpenCL, CUDA, etc.) but are still visible in GPU monitoring tools likeGPU Shark:

The trick to enabled all cards, is to fool Windows with a dummy VGA dongle.

This VGA hack require one DVI to VGA dongle and three resistors. Any resistor from 50 to 150 ohms can do the job.


4 of 18 7/7/2011 1:22 AM

I found in my stock of electronic components, three 150-ohm resistors for the first VGA dongle. For the second I used two100-ohm and one 120-ohm resistors.


5 of 18 7/7/2011 1:22 AM

the VGA hack with three 150-ohm resistors

As soon as the dongles are plugged, Windows enables the cards. Here is the second card in CCC:

Catalyst Control Center, primary card enabled

And in GPU Caps Viewer, OpenCL properly lists the three GPUs as OpenCL devices:


6 of 18 7/7/2011 1:22 AM

GPU Caps Viewer, all Juniper GPUs are listed

Now youre ready to use any multi-GPU capable applications with a single monitor!

In the following screenshot, the first GPU processes all OpenGL render calls, while the second and third GPUs process theOpenCL code.


7 of 18 7/7/2011 1:22 AM

GPU Caps Viewer, all Juniper GPUs are listed

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Related posts:

[VGA Hack] How To Make a VGA Dummy Plug1.[TEST] GPU Computing GeForce and Radeon OpenCL Test (Part 4 and Conclusion)2.


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[Test] Hybrid Systems: Radeon HD 6950 for 3D and GeForce GT 240 for OpenCL3.(Test) OpenCL Support Gets Better and Better4.[Tested] oclHashcat 0.2.4 GPU-based Cracker: OpenCL / CUDA Test5.

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10 comments - What do you think? (3,418 views) Posted by JeGX - June 22, 2011 at 2:17 pm

Categories: GPU Caps Viewer, OpenCL, Test Tags: dummy, gongle, gpu caps viewer, graphics card, hack, opencl, radeon hd5770, test, vga

10 Responses to (Test) Dummy VGA Dongle with Win7: Three Radeon HD 5770 and a SingleMonitor (VGA Hack)

MFA says:June 22, 2011 at 3:33 pm

pure win!

1.

AAmax says:June 22, 2011 at 5:00 pm

What do you mean disabled if not connected to a monitor, how then they do it for Physx, they use one fast Radeonand one poor Geforce just for Physx, or was this disabled?

2.

AAmax says:June 22, 2011 at 5:14 pm

Separate run on each Radeon then just say saw, very interesting. Not parallel, each unit its own run, this is server typestuff.

3.

JeGX says:June 22, 2011 at 5:37 pm

I just tested with one HD 5770 + one GTX 260 + one GT 240 and without the VGA hack, both GeForce are listed inthe OpenGL section of GPU Caps Viewer.

Then this VGA hack is mainly useful for Radeon cards.

4.

Leith Bade says:June 23, 2011 at 3:52 am

At least in Linux you can enable OpenGL on cards with no screen with a simple X server config hack.

5.

WacKEDmaN says:June 23, 2011 at 7:46 am

amd need to add support for headless cards to their driver

6.


9 of 18 7/7/2011 1:22 AM

nvidia managed to do it..

ca$per says:June 23, 2011 at 7:54 am

Does disabled cards consume much power? I mean when used without dongle.

7.

Leith Bade says:June 23, 2011 at 9:41 am

The fan keeps spinning so I would say so. They would need a special switch on the cards power input to be able toturn a card off completely but they dont bother as it is not like you can hot swap PCI cards.

8.

ca$per says:June 23, 2011 at 9:45 am

Hmm So i presume its just in idle state. Thanks.I guess if i need to test some app on Nvidia card and on ATI card, to ease the process i can simply insert both cards inmy PC and then just switch the monitor to one or another and simply relaunch the application?

9.

Athlonite says:July 1, 2011 at 9:00 am

this the same hack as used by use HDxxxx users to get F@H running before they fixed the CF problem

10.

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dummy vga dongle

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