Troubleshooting Multiple gpu setups that use Riser cards

Ian&Steve C.
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most PCIe risers will be

most PCIe risers will be listed in centimeters, so make sure to do the conversion.

 

I use 20cm risers for all but the "bottom" PCIe slot (the one furthest from the CPU socket. for that one I use a 30cm riser.

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San-Fernando-Valley
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LINKUP TECHNOLOGIES 

LINKUP TECHNOLOGIES  (https://linkup.one/)  has many nice (expensive) ones ...

solling2
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Ian&Steve C.

Ian&Steve C. wrote:

(...)

I've been down this road. I've made this mistake. You might get away with it for a while, but eventually the heat generated from pulling such high current over such cheap cables (those adapters SATA-PCIe adapters are chinese garbage, they take a SINGLE 12v lead and just split it to two pins on the PCIe connector) eventually you're going to melt a connector at best, or start a fire at worst.

Like I said, I've done this. it ran "fine" for some months, until while troubleshooting i discovered one of the connectors was melting. I never went back to this setup after that. that was when I was mining with 8x RX570s (before I really started getting into BOINC, I sold these off for nvidia cards back in like 2018).

If you're dead set on using these SATA leads, run only a max of two risers per peripheral cable from the PSU and get yourself some SATA or Molex adapters that use TWO connectors per ONE PCIe (like this: 2xSATA to PCIe).

I'm still highly recommending that you do it the right way though and get a second PSU for more PCIe connectors. You'll thank yourself later.

Thanks for the clarifications concerning PC cables. May I ask though what is meant by the last sentence? Is the second PSU going to replace the smaller one or is there a way to use two small PSUs to supply one demanding system?

Tom M
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Ian&Steve C. wrote: most

Ian&Steve C. wrote:

most PCIe risers will be listed in centimeters, so make sure to do the conversion.

I use 20cm risers for all but the "bottom" PCIe slot (the one furthest from the CPU socket. for that one I use a 30cm riser.

14" -> just under 36 cm.

I know I am using a smaller (from the external width of the mining rack than average. But the brand of ribbon extenders you have pointed me to as being reliable, doesn't seem to offer a longer than 30 cm riser.

It may be I will have to migrate back to my "longer" mining rack (which is also not as tall) to get a 30 cm riser to be long enough?  It sounds counter intuitive though.  Where is my tape measure?

Tom M

Over the hill?  What hill?  I don't REMEMBER any hill...
A Proud member of the O.F.A. (I've forgotten what that stands for.... ;)

 

 

 

 

San-Fernando-Valley
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@Tom M: are you talking

@Tom M:

are you talking about "riser cards" or "riser cables"   ---   I'm getting confused ...

Ian&Steve C.
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Tom M wrote:Ian&Steve C.

Tom M wrote:

Ian&Steve C. wrote:

most PCIe risers will be listed in centimeters, so make sure to do the conversion.

I use 20cm risers for all but the "bottom" PCIe slot (the one furthest from the CPU socket. for that one I use a 30cm riser.

14" -> just under 36 cm.

I know I am using a smaller (from the external width of the mining rack than average. But the brand of ribbon extenders you have pointed me to as being reliable, doesn't seem to offer a longer than 30 cm riser.

It may be I will have to migrate back to my "longer" mining rack (which is also not as tall) to get a 30 cm riser to be long enough?  It sounds counter intuitive though.  Where is my tape measure?

Tom M

i think we have the same size rack. yours holds a 6 GPUs by default, with 5x 120mm fans in front of the GPUs? if so that's the same as mine. some basic measurements, the whole rack is 25-1/4" wide and the GPUs sit 6-1/2" above the motherboard surface. and after looking at my rack again, the two furthest GPUs are using the 30cm cable. not just the last one. 

 

here's my 7x 2080ti system as an example/visual: https://imgur.com/a/8zSp4EQ

these are EVGA RTX 2080ti XC Ultra cards, 2.75-slot width

cards are power limited to 225W

temps stay about 60-65C while crunching the toughest projects (GPUGRID)

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Ian&Steve C.
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San-Fernando-Valley

San-Fernando-Valley wrote:

@Tom M:

are you talking about "riser cards" or "riser cables"   ---   I'm getting confused ...

cables, but there are two types of cables. "Ribbon" style and "USB". Tom is using the USB style, I use the ribbon style. Ribbon style is more expensive, but you get less cable clutter, and more PCIe bandwidth, and in some cases, more reliability since the USB cables can be fincky. USB-style has a benefit of removing the power reliance from the motherboard. they have external power input for slot power, the ribbon risers need to get the power from the board most of the time.

USB:

Ribbon:

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Ian&Steve C.
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solling2 wrote: Thanks for

solling2 wrote:

Thanks for the clarifications concerning PC cables. May I ask though what is meant by the last sentence? Is the second PSU going to replace the smaller one or is there a way to use two small PSUs to supply one demanding system?

you can use two PSUs to distribute the load to different components. they make splitters/adapters that allow you to power on two PSUs simultaneously. having a second PSU also gives you more physical connectors as most PSUs wont have enough to power many cards AND risers.

adapter:

 

or in my case, since my secondary PSUs are HP server PSUs, I use what is referred to as a "breakout board" that gives me a bunch of PCIe connectors, and it has a small SATA lead for power on detection of the main PSU and triggers it to power on.

 

you can also just turn on the secondary PSUs manually, power on the secondaries first, then the main PSU.

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Tom M
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Excellent show and tell,

Excellent show and tell, Ian&Steve.

Tom M

Over the hill?  What hill?  I don't REMEMBER any hill...
A Proud member of the O.F.A. (I've forgotten what that stands for.... ;)

 

 

 

 

San-Fernando-Valley
San-Fernando-Valley
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... great answer!! Many

... great answer!!

Many thanks for such an elaborate post.

 

But, the power reliance from the board is only needed with GPUs that don't have a discret/own power connector.  Or am I wrong with this assumption?

 

Again thanks:   Ian&Steve C.

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