HP Z620: installing a third graphics card

[xberg]

Hi,

I would like to add a 3rd graphic card on my HP Z620. 

The HP Z620 comes with only 2x 6 pin PCI-E cables to power graphic cards. 

Any thought as to where I could get another 6 pin power connector? I had a quick look at the PSU but found no available 6 pin PCI-e connector.

Using a molex or sata converter seems like a REALLY bad idea if I don't want the whole rig to burst in flames 🙂 

thanks!

[Brian1965]

Hi xberg,

What grapics cards are you looking to install?

If you look at my previous post (part 1) you will see a table listing the HP Z620 graphics 'constraints', i.e. maximum power, slots, etc.

The Z620 can support up to 4 graphics cards but only in specific configurations due to power limitations. However, I believe there is some 'wiggle' room regarding the total power of all the GPU cards combined, but caution must be exercised. At your own risk.

I'm sure you're already aware, but if the card is 75W or less, then you do not need auxilliary PCI power, i.e. the card is powered from the PCI slot.

[xberg]

Hi Brian,

I'm about on the same page as you. I was just wondering whether you found a 3rd PCIe cable somewhere 🙂

So far I successfully:

Ran a single R9 Fury which requires 250W (using both PCIe cables). Very stable.

Ran a single GTX 1080 (190W) using a single PCIe 8 pin cable (a bit dodgy as I'm using a 6 to 8 pin converter: 6 pin provides 75W and 8 pin provides 150W, but with the convertor is not a true 8 pin cable). Still far from the recommended 300W. This is stable.

Next test is the GTX 1080 + GTX 1060 (120W) taking it to the limit of 300W.

Note that the 300W comes from the fact that each 6 pin PCIe delivers 75W + 75W from the board. But my config is not balanced so I'll see if it works.

I guess in the absence of a hidden 8 pin PCIe I'm stuck with only 2 cards. 

Yesterday following the power cables out of the PSU I found one labelled G3, but I think this just brings the cables to G1 and G2. 

[SDH · Accepted solution]

I believe you are underestimating significantly the power capabilities of your two supplemental power cables.

You can download the latest (v5) Z620 technical and service manual for slot capabilities from HERE , and also could look directly on the label on your Z620's power supply.... the ATX standard you are using is lower than what HP uses for the two 6-pin supplemental PCIe power cables in the Z620.  By quite a lot.  The exact rated amperage for those two HP cables were not in any manual I've found, but are available right there on the label.  I agree on the two PCIe x16 "video" slots providing 75W up to the card.  Other slots won't have that same power capacity.  Note the small writing on the label that total 12V DC is not to exceed 800W, and they tell you all the items to sum.  If you use SSDs instead of HDDs you free up some wattage towards the total, and same idea if you are using 1 instead of 2 processors.

Here's a quote from a past post:  "The Z620 power supply is easy to release and rotate out so you can see the amperage label on the top for the different cables.... those two auxiliary PCIe power cables the OP showed in his original picture are "G1" and "G2" both on the plug end and the power supply label.  Each of G1 and G2 are rated on the power supply specs label at 18A 12V.  That's a lot of watts worth of power available through each cable if you do the math."  To save you from digging into your case here is that Z620 power supply label:

HP has 6 pin to dual six pin adapters and also 6-to-8 pin adapters that are engineered to do what you need (see link below).  You're looking at those two cables as garden hoses when they could be thought of as two fire hoses.  There is a broad range of quality of adapters for the plug ends..... the HP ones will be engineered to the top level.

Look  HERE for added info, and there are a couple of added links in that one that will get you to more details.  We've posted in the forum here on the HP part number for at least the official 6-to-8 HP adapter.

https://h30434.www3.hp.com/t5/Business-PCs-Workstations-and-Point-of-Sale-Systems/really-only-1-6pin...

[xberg]

Wow. That is amazing!

I really love what HP have done with this station 🙂 

For some reason your photo was not attached: would love to see it and see this 18A. 216W on a single 6 pin is indeed amazing.

thank you for sharing so much knowledge!

[Brian1965]

Thanks for the detailed info SDH, my PSU label isn't exactly easy to access. I knew they could handle more than standard aux. PCI leads but not the specific amperage/power limits.

I did run my Z620 with a Quadro K4200 (108W) and M2090 (225W) previously and I only used one aux. PCI cable per card so effectively pulling 150W from a single aux. cable.

 Still, it's a little strange that HP recommends the total power of all graphics cards cannot exceed 300W. Talk about having a 'safety margin', (not a criticism of HP, maybe a bit over cautious?).

[xberg]

I love your metaphor about the garden hoses and the fire hose. Well done: have been thinking about that since I first read your notes.

I do wonder on the other hand if there is indeed any magic sauce at all in their splitters or connectors. Right now I use Chinese-sourced 6-pin to 8-pin converters. I wonder if a standard 6 pin to dual 6 pin would work or would burn the workstation. 

I think the magic sauce is in the PSU hand putting 18A in there. Afterwards it's just cabling. But maybe not 🙂 The only thing I could see is using a slightly thicker cable. 

Fascinating workstation... 

[SDH]

Happy to help.  This issue has been ongoing for years now, and I sure wish HP would put out a white paper on it, plus provide a HP quality easily found (1) 6-pin to two 6-pin and (2) 6 pin to 8 pin adapter.  I've never found the HP 6-pin to two 6-pin adapter part/option numbers, but here is the most recent version from HP (option number N1G35AA), and a source that has 3 available in stock for about 25.00 (!),  HERE.  The actual SP and AS HP part numbers have been posted in this forum in the past to help searching.

Regarding pictures in posts.... they'll only become visible when a moderator releases them.... check back in a bit.

Two added links, and this is still going on in the Z840s as you'll see.  I am sure those 6-pin cables are super-powered too.

HERE  and  HERE

Added in:  Below is a pic of the label from the Z840's 1125W power supply.... it appears to have 4 total PCIe supplemental power cables (G1-G4), all 18A too:

[SDH]

And, just for fun, below are the two power supplies for the Z820, one of which is the lower powered 850W version, and the other is the higher powered 1125W version.  You may know that the first has two PCIe supplemental 6-wire power cords, and the second has three.

You can see those in the two images below as G1/G2 and G1/G2/G3, all of which are 18A:

[DGroves]

this might help  to read a power supply's real wattage since some supplys are single rail and some like the z workstations are multi rail

also the the tempture the ratings are speced for vary by power supply mfgr with some being specced at a very low (cool) tempture instead of the real (hot) temps actually found inside a systems case

Maximum Power

Power supplies are basically differentiated by output wattage, which is quoted according to the "Maximum Power" output. Maximum power is not just a number, it also gives a basic idea of how many devices (and what type of devices, in terms of power consumption) the power supply will be able to feed.

However, the maximum power figure alone is not enough to determine whether a PSU is able to drive your computer. Each voltage rail requires attention, but the most attention needs to go to the +12V rail(s), since the processor and PCIe video cards receive their power from them. The power supply must output at least 18A (amps) on the +12V rail(s) for a mainstream up-to-date computer; more than 24A for a system with a single enthusiast-class graphics card; and no less than 34A when it comes to a high end SLI/CrossFire system. The output amperage figure we're talking about here is the combined figure for PSUs offering more than one +12V rail. Of course, it is the combined total output number you should look for, and you can't always add up the+12V rails to calculate the combined output. For instance, a PSU labeled with rails labeled +12V1@18A and +12V2@16A may only have a 30A combined power output instead of 34A. Look for this information in the detailed item specifications or on the PSU information label.

If you are going to run an SLI/Crossfire configuration, please make sure the +12V rail(s) provide no less than 34A combined. Different power supplies are labeled differently – some show the maximum amperage provided by each rail, and some will provide the maximum combined maximum wattage, e.g. 396W, which is equals to 396W/12V = 33A.

Continuous and Peak Power

Please note that continuous power and peak power are different. Generally, the "Maximum Power" figure of a power supply refers to the continuous (stable) power the PSU will deliver consistently, while the peak power refers to the elevated maximum (surge) power the PSU can deliver, albeit for very short amount of time (e.g. 15 seconds).