HP Z840 with 3 GPUs, Power Configuration Help

[4zain4]

Hellow everyone!

So, I have the Z840 with the 1125w PSU currently & a EVGA 1070 FTW . I want to add two 1080ti to the setup, However I can see  three male 6 pin connectors (named G1,G2,G3) and each GPU has dual 8 pin on them, what would be the solution in this case? do I get a 6 pin to dual 8 pin splitter and use the three 6 pins.. each feeding single GPU? or there is another setup for such configuration? On the specs, this WS does support up to 3 GPUs with the upgraded PSU 

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[DGroves]

not a HP recommend configuration, the 1080TI pulls close to 250/260 watts the 1070 around 150 watts

this is a total of 570 watts just on the GPU rail

note that SLI is not supported on any nvidia consumer cards, so your apps will have to be CUDA aware and you may have to configure the bios to enable the compute option for PCI-E SLOTS THAT HAVE cards THAT ARE NOT BEING USED FOR VIDEO

DO NOT ENABLE COMPUTE FOR ALL SLOTS, or any slot  that has (or will have) a card used for video output

enabling the compute option tells the system that the video card in this slot is not a active display device, and to shutdown the video leaving only the cards Compute functions (IE- CUDA) active

the issue is the z820pwr supply is a multi rail design (not single rail) and 570 watts on the GPU rail is at the max limits

please read the HP z820 SERVICE MANUAL for more info and hp recomended slot placement for multiple video cards

you will also need High quality six to eight pin adapters i recommend the HP ones as 3rd party ones can vary wildly in quality

the z820 has three  6 pin gpu connectors, you want to split the 180TI pwr so each card is using one GPU 8 pin adapter per pwr supply connector and the 3rd gpu six pin uses adapters to split the single six pin into 3 (one for the 1070) and one each for the 1080TI's 

note that the thermals of 3 video cards will cause the system fans to ramp up in speed to a high level, you may also have to ramp up the default min fan speed to a higher setting, this is not a setup i recommend for a 24/7 basis (although short term might be ok)

[4zain4]

Thank you for your reply. I do have some questions if you don't mind asking:

*The system I have is the Z840 not Z820. Does this make any difference?

* If I use the power connection as described by you, then the 1070 will receive  only one 8 pin connection and it requires 2. Is there any spare 8 pin / SATA I could use?

* Yes thermal situation will be another issue.. I am planning to keep the side cover open till I manage to come up with a proper solution.

[Brian1965]

Hi 4zain4,

What is your local mains voltage? This determines the maximum power that the HP Z840 PSU can supply, e.g.

1125W 90% Efficient wide-ranging, active Power Factor Correction

NOTE: The 1125W (1450W at 200V Input Voltage) power supply can also supply 1275W of output power when the input voltage is greater than 105V. If the input voltage is less than 105V, but greater than 90V for any reason, the maximum power that can be drawn is 1125W. An uninterruptible power supply (UPS) is highly recommended if 1275W output power is desired.The 1125W Power Supply can also supply 1450W of output power when the input voltage is greater than 200V under all conditions.

FYI - https://support.hp.com/gb-en/product/hp-z840-workstation/6978842 

Lots of handy resources, e.g. maintenance and service guides, drivers, etc. I recommend you download and familiarise yourself with the Maintenance and Service Guide Manual and Z840 Quickspecs.

[4zain4]

Hello Brian,

220v to 240v

[Brian1965]

Luckily, you may be in with a chance of running 3 high -end GPU's in the Z840, but first please make sure you are happy to proceed, e.g.

1. The HP Z workstations do not support SLI configurations, (i.e. as used for high end gaming). You will only be able to utilize all the GPU's if your software supports multiple GPU rendering or additional compute cards, e.g. CUDA processing - Video rendering, scientific simulations, FEA, etc.

2. As mentioned in previous posts, this configuration is not supported by HP and you will be pushing the PSU quite hard under full GPU load, but I believe within an acceptable margin since your mains supply is >200v (=1450W PSU). (I'm guessing your UK based, like myself). This configuration may invalidate any remaining HP warranty.

If you're still happy to proceed then it will be at your own risk. I know that the HP Z820 and HP Z840 share a similar PSU specification, and from the HP Z820 PSU label;

G1 - G3 are rated at 12v, 18A  = 216W power each.

The Z820 supports upto three 225W cards = 675W in total! I expect this will be similar for the Z840.

With 1x 1070 (150W) + 2x 1080ti (250W) = 650W in total.

What you need are 2off, 6-pin to 2x 8-pin PCI auxilliary power adapters to power the 2off, 1080ti cards. e.g.

Make sure you only use high quailty adapter cables. They should be as short as possible, and have a heavy gauge of wire to handle the high power. Cheap cables have been known to be very unreliable, and can cause errors during boot-up, i.e. missing auxilliary power on the GPU(s).

I have used the above adapters to power a Tesla M2900 card (225W) in my Z620 in the past without any issues, from a single 6-pin PCI auxilliary power connector. The PCI slot provides 75W, with the remaining power being supplied via the PCI auxiliary power cable(s).

[4zain4]

Thank you for the great input!

This WS will be used for CUDA cores rendering, so no SLI required. Warranty has expired, so experiments should start soon

I used to live in London and now I am in UAE & true both on 230V.

As for the splitters , I found 6pin to dual 8pin splitters on Amazon, However I noticed (from the pictures) that one for the pins on the splitters has a square shape while the opposite one on the HP 6pin has a chamfered square shape... will this cause any issue?

[Brian1965]

Can you post a link to the adapters you found on Amazon?

[4zain4]

Please see below photo

[4zain4]

https://www.amazon.ae/Graphics-Express-Y-Splitter-Extension-TeamProfitcom/dp/B07C35YR6V/ref=sr_1_3?k...