Dummy Load for Second GPU (Vista Requirement)

[KE1HA]

Hey All,

I've just purchased a couple more 9800 cards and want to put them into a headless node for GPU F@H.

It's my understanding, (which could be out to lunch), that in order to do this on Vista, one must have a monitor (or at least the impression of a monitor) present on both cards in order for it to perform.

I did some quick SVGA measurements and found what I think is the right combinaiton to put a dummy load on one, if not both cards, once they are configured correctly.

Male side of the cable:

(RGB) - 75 Ohm between pins:
1 and 6
2 and 7
3 and 8

(SYNC) 600 Ohm between pins:
10 and 13
10 and 14

SVGA Source: SVGA Pin-Out

So in theory, one could pop resistors in an aftermarket gender bender, and this would emulate the presence of a monitor for one if not both cards yes?

If there's a better way to present the monitor, without actually having it attached, or if my understanding of the need for a second monitor is in error, please advise.
.

 

[verbal]

Lots of people have made a 'VGA dummy' preciesly for this purpose.

Here´s mine

You only need the resistors for the RGB wires. Here´s a page with instructions..

http://soerennielsen.dk/mod/VGAdummy/index_en.php

If you are planning on having this folding box headless you will need to run something like Tight VNC to remote into it as windows remote desktop will kill the current WUs each time you use it.

 

[KE1HA]

Thanks verbal, That's EXACTLY what I was thinking about, guess I should have google'd it first .. LMAO

I'm probably going to map out the DVI to VGA pins, so I can just add the resistors to the DVI connector (if I can find a shell that can be opened)

I'm was going to share the folders and monitor it from FahMon. If I need to get into the nodes themself, will have a MN / KB / MS available at the rack.

VNC isn't a bad option though, will look into that.
.

 

[KE1HA]

A simplified way:

Source: Digital Visual Interface Wiki. Wiki

The DVI connector usually contains pins to pass the DVI-native digital video signals. In the case of dual-link systems, additional pins are provided for the second set of data signals.

As well as digital signals, the DVI connector includes pins providing the same analog signals found on a VGA connector, allowing a VGA monitor to be connected with a simple plug adapter. This feature was included in order to make DVI universal, as it allows either type of monitor (analog or digital) to be operated from the same connector.

The DVI connector on a device is therefore given one of three names, depending on which signals it implements:

DVI-D (digital only)
DVI-A (analog only)
DVI-I (integrated, digital & analog)

The connector also includes provision for a second data link for high resolution displays, though many devices do not implement this. In those that do, the connector is sometimes referred to as DVI-DL (dual link).

Most all of the cards we're using for FAH are of the DVI-I varity, meaning they carry Primary + Secondary Digital signals with the inclusion of Analog (VGA in our Case) signals, thus the reason we're able to terminate / load the VGA portion with the D-Sub DVI to VGA gender changer.

As verbal provided, if we load pins 1-6, 2-7 and 3-8 (R-G-B) this satisfies the need for Vista, however, there is no need to use two connectors, we merely map / load (75 Ohm Resistors) a DVI-I or DVI-A D-Sub connector Pin's C1(R), C2(G) and C3(B) with Pin C5(GND) and we're done. DVI-D type connectors will not work as they do not provide for Analog signal processing.

Pin-Out:
Pin 1 TMDS Data 2- Digital red - (Link 1)
Pin 2 TMDS Data 2+ Digital red + (Link 1)
Pin 3 TMDS Data 2/4 shield
Pin 4 TMDS Data 4- Digital green - (Link 2)
Pin 5 TMDS Data 4+ Digital green + (Link 2)
Pin 6 DDC clock
Pin 7 DDC data
Pin 8 Analog vertical sync
Pin 9 TMDS Data 1- Digital green - (Link 1)
Pin 10 TMDS Data 1+ Digital green + (Link 1)
Pin 11 TMDS Data 1/3 shield
Pin 12 TMDS Data 3- Digital blue - (Link 2)
Pin 13 TMDS Data 3+ Digital blue + (Link 2)
Pin 14 +5 V Power for monitor when in standby
Pin 15 Ground Return for pin 14 and analog sync
Pin 16 Hot plug detect
Pin 17 TMDS data 0- Digital blue - (Link 1) and digital sync
Pin 18 TMDS data 0+ Digital blue + (Link 1) and digital sync
Pin 19 TMDS data 0/5 shield
Pin 20 TMDS data 5- Digital red - (Link 2)
Pin 21 TMDS data 5+ Digital red + (Link 2)
Pin 22 TMDS clock shield
Pin 23 TMDS clock+ Digital clock + (Links 1 and 2)
Pin 24 TMDS clock- Digital clock - (Links 1 and 2)
C1 Analog red
C2 Analog green
C3 Analog blue
C4 Analog horizontal sync
C5 Analog ground Return for R, G and B signals

Conclusions:

All we should need is a DVI-A or DVI-I D-Sub Connector, D-Sub Hull, and 3x 75 Ohm Resistors.

These are all readily available in your local Electronis supplier stores, I found them on the UK links first before looking in the US.

Will do this mod over the weekend and let you know if I've not fried my new Card
.

 

[rich99million]

I guess it just depends on what you can find more easily, DVI-VGA adapters tend to come included with cards and I'm betting that a 15-pin D-sub is going to be cheaper and more easily available than a DVI D-Sub.

Definitely a much neater solution to do it directly though of course


edit: Ok so I'm wrong then, just checked my usual high-street electronics components shop (probably a competitor due to other products) and the DVI connectors are £1.49 as opposed to £1.59 for a 15-pin HD D-sub

 

[Snapshot]

I think the VGA D-sub will be easier to solder. And I couldn't see hoods for the DVI connector on that site although they may not be in the connectors section, of course.

 

[KE1HA]

I found them both locally, but they are a bit costly, about 3.50 USD for the connector and 4.50 USD for the hood. There's plenty of room for the resistors, and I'm probably going to pull or trim off the pins that aren't needed.

Just waiting on the 2 9800's to show up. This is going to make a very cheap, but HIGH PPD folding machine as there going on my E6600 set-up.
.

 

[rich99million]

I think the VGA D-sub will be easier to solder. And I couldn't see hoods for the DVI connector on that site although they may not be in the connectors section, of course.

I was thinking that the DVI connector might fit into a standard 15-way hood - certainly would be about the right size and would explain why they don't seem to stock them specifically.

 

[KE1HA]

I can't post the links here for obvious reasons, but they look to be standard, allthough, the hoods are called out specifically for the the respective DVI connector. Only thing I see different is the cable diameter options, 8.5mm and 9.5mm

 

[Delboy]

I'm about to setup 3 GPUs on one mobo running vista. So if I get this straight, I either need to plug in 3 monitors or build one of these to make the cards think they are displaying on a monitor (one for each GPU) - is that right? Can I plug one monitor into the first card, get it going then move the monitor along? Or does this need to be in place the whole time the card is folding? I plan on using the console versions of the applications in each case, do I still need to do this?

Appreciate any help.

 

[KE1HA]

From my understanding, on Vista, you have to have the presence or simulated presence of a monitor connected for the output to be enabled.

So, and those of you in the know, please correct me if Im wrong here, you'd need a load on all three cards for them to function, either a physical monitor connection or one of these load devices we're talking about here.

I dont think this is an issue with Win-XP.

EDIT: Im not sure about the sart up of all the cards yet, as this is the first time I've messed with Multi-GPU folding. Will let you know when I've sorted it out.
.

 

[verbal]

The reason for faking the presence of a monitor is so that the windows desktop can be extended onto these other 'monitors'.

However it may be the case that the very latest Nvidia drivers no longer require cards to have monitors connected for CUDA to work. I haven't got time to check this but I think I read it on the folding forum.