HP Z440 not allowing SLI with two Quadro P5000

[TadHarms]

Hello everyone,

We have several Z440 workstations that we recently installed two Quadro P5000 video cards in each.  Using the Nvidia control panel, we are not given the ability to enable SLI.  If the SLI bridge is removed the Nvidia control panel reflects this by giving a message stating "A higher performance SLI bridge can improve your experience."  but once reconnected the message goes away but still have to option to enable SLI.  Other then the video cards nothing in the systems have been changed.  They are standard Z440 workstations.  Please let us know any info!

 Troubleshooting steps we have attempted:

1. Updated all system drivers
2. Updated firmware on the P5000 cards
3. Updated BIOS
4. Removed and cleaned video drivers and reinstalled
5. Attempted to use both older and newer drivers
6. Used multiple sli bridge connectors
7. The P5000 cards have two SLI connections "SLI 1" and "SLI 2" we have tried to connect both SLI 1 and SLI 2 at the same time, as well as only one at a time.  

[iMaxx]

I beleive you need a High Performance SLi birdge like this.
The old fasioned ribbons won't work.

[DGroves]

the P5000 card is not a listed as a "approved" card for the z440 in the HP quickspecs

and if using two cards, i beleive you require the optional 700 watt supply instead of the stock 525 watt unit

http://www8.hp.com/h20195/v2/getpdf.aspx/c04400038.pdf?ver=1.0

https://www.nvidia.com/object/sli-certified-systems-and-motherboards.html

consumer systems use a hardware chip on the motherboard to activate SLI features,

HP systems do not have/use this method, so they most likely use a "whitelist" of preapproved cards stored somewhere

(perhaps in the bios) if this guess as to how SLI activation works is true and your model is not in the list, then SLI will not be available.

if anyone knows how HP actually checks for SLI, please post, but if your are taking a guess like i am please note that it's a "guess"

[TadHarms]

I appreciate the follow up!  I am inclined to agree, the Nvidia control panel shows the two cards independently and states to maximize performance by using SLI.  After installing the SLI bridge the message goes away so the system is seeing that the cards are connected but is not able to activate.  As DGroves mentioned if anyone knows what aspect of the system checks this info or if there are any work arounds we would be happy to give them a try.  We have plenty of systems to test with.  

[DGroves]

in reguards to the SLI bridges,nvidia has this to say about the old vs new performance SLI bridge

Nvidia says the New HB Bridge will transfer data at 650MHz on GeForce GTX 1080 cards compared to the 400MHz that older GeForce cards achieve with soft ribbon style bridges, such as those that come bundled with a motherboard or GPU.

The older soft bridges will still work, but only up to a point. You can also use the aftermarket fancy SLI bridges that sold with the last gen of cards, but even those won’t achieve maximum potential, according to Nvidia.

based on nvidia's statements and the "OP" post that the system is seeing two cards and mentioning SLI can improve performance, which disappears when a SLI bridge is installed, the SLI bridge is not the issue in getting SLI activated with quadro cards not in HP's pre approved list. this reinforces my guess that HP is using a white list in the computers bios to only allow SLI activation with the card models that HP has tested and paid a license fee to nvidia for SLI usage

the problem is that currently there is no known method of getting a modified HP workstation bios to be flashed since the system checksums the new bios through a checksum routine before allowing the new bios to be written. modded bios's will fail the checksum and not be writen. this leaves modding the video driver itself, which has been done in older drivers, but the current drivers appear to be very hard to modify as nvidia has closed up the previous methods that modders used to bypass the SLI checks