Question Need info on molex pcie risers for mining psu on how they take power "diagram" like

[JonasTechButchery]

So I would like to know does molex riser pcie consume power only from 12v and 5 v is for show or does it use /need/require both to be plugged in? I intend to retrofit a very expensive Silverstone modular 1300R PSU who's voltage has weakened on 5v compartment but 12v is perfect. The PSU will be converted to be pure 12v 6/8pins/molex and work as secondary PSU for dual PSU chained build mining/server type purpose.

But since molex has 5v pin that is what worries me. Do I need 2 gnd wires for pci riser molex to be safe to use or 1gnd is fine (2pin molex like one used for fans)

Can I do this on HP server breakoutboard too? It has 12v and GND area that's how it gives out all power. Solder 1 molex wire on 12 and one on GND and use for pci risers? or am I missing something like overheating, current resistance? IDK... thus I am asking if somebody could offer his deeper knowledge of this. Any additional intel means a lot. Thanks

Please don't even use word RMA if that was an option I would have done it. Every time I ask a question there is somebody telling me to RMA like I don't know how warranty works. RMA is not an option here. DIY or garbage. It's too expensive to throw away so DIY...

 

[Aeacus]

So I would like to know does molex riser pcie consume power only from 12v and 5 v is for show or does it use /need/require both to be plugged in?

GPU riser cards (be it vertical mount in gaming rig or mining rig), work only with 12V. 5V isn't needed at all.

Riser mounts can have two types of input power connectors, either 4-pin MOLEX (what you have) or 6/8-pin PCI-E. And in PCI-E, there is no 5V what-so-ever.

a very expensive Silverstone modular 1300R PSU

That is a joke. Sliverstone HELA 1300R is actually one of the cheapest 1.3kW units out there. At ~280 bucks, it doesn't get even close to the actual, very expensive 1.3kW units. E.g like these beauties,
pcpp: https://pcpartpicker.com/products/compare/4GyV3C,HyYmP6,hMCZxr,WrcgXL/

Just look what Seasonic units cost. Now, those are expensive. Also, best what money can buy as well, hence the price.

Do I need 2 gnd wires for pci riser molex to be safe to use or 1gnd is fine

One ground is fine IF you do not exceed the wattage capacity of 4-pin MOLEX cable. The 2nd ground is for 5V in 4-pin MOLEX cable.

2pin molex like one used for fans

If you use that, the cable wires are so thin, that it won't survive powering the riser. ~30W is what the 2-pin fan cable is capable of, since it is ever used only for up to 12W to power the case fans.

Solder 1 molex wire on 12 and one on GND and use for pci risers? or am I missing something like overheating, current resistance? IDK...

Ideally, you'd have one 4-pin MOLEX cable per riser. At most, you can get away with two risers per one 4-pin MOLEX cable. But if you plan to solder the 4-pin MOLEX cable longer with more connectors, e.g 6, to power all risers with just one MOLEX cable, you WILL melt the MOLEX cable.

4-pin MOLEX cable is rated up to 156W. One riser consumes 75W. So, MAX two risers per one cable (total 150W per one cable). Ideally, each riser has it's own cable coming from PSU.

E.g like this dual-PSU 6x GPU mining rig:

Direct link if image doesn't load: https://blogger.googleusercontent.c...WHLnwYiQG3tYRWE8ojNW49oTBo/s1600/powerrig.png

Please don't even use word RMA if that was an option I would have done it. Every time I ask a question there is somebody telling me to RMA like I don't know how warranty works. RMA is not an option here. DIY or garbage. It's too expensive to throw away so DIY...

I would've suggested new PSU instead, since your HELA R seems to be on it's way out. And if it's older than 5 years, then it's warranty is also expired (hence no RMA option). Also, it being one of the cheapest 1.3kW units, doesn't make it too expensive to throw away.
Now, if you'd have 500+ bucks Seasonic unit, then it would be different story. And even then, you could just RMA Seasonic unit since that one comes with 12 years of warranty.

 

[JonasTechButchery]

GPU riser cards (be it vertical mount in gaming rig or mining rig), work only with 12V. 5V isn't needed at all.

Riser mounts can have two types of input power connectors, either 4-pin MOLEX (what you have) or 6/8-pin PCI-E. And in PCI-E, there is no 5V what-so-ever.


That is a joke. Sliverstone HELA 1300R is actually one of the cheapest 1.3kW units out there. At ~280 bucks, it doesn't get even close to the actual, very expensive 1.3kW units. E.g like these beauties,
pcpp: https://pcpartpicker.com/products/compare/4GyV3C,HyYmP6,hMCZxr,WrcgXL/

Just look what Seasonic units cost. Now, those are expensive. Also, best what money can buy as well, hence the price.


One ground is fine IF you do not exceed the wattage capacity of 4-pin MOLEX cable. The 2nd ground is for 5V in 4-pin MOLEX cable.


If you use that, the cable wires are so thin, that it won't survive powering the riser. ~30W is what the 2-pin fan cable is capable of, since it is ever used only for up to 12W to power the case fans.


Ideally, you'd have one 4-pin MOLEX cable per riser. At most, you can get away with two risers per one 4-pin MOLEX cable. But if you plan to solder the 4-pin MOLEX cable longer with more connectors, e.g 6, to power all risers with just one MOLEX cable, you WILL melt the MOLEX cable.

4-pin MOLEX cable is rated up to 156W. One riser consumes 75W. So, MAX two risers per one cable (total 150W per one cable). Ideally, each riser has it's own cable coming from PSU.

E.g like this dual-PSU 6x GPU mining rig:

Direct link if image doesn't load: https://blogger.googleusercontent.c...WHLnwYiQG3tYRWE8ojNW49oTBo/s1600/powerrig.png


I would've suggested new PSU instead, since your HELA R seems to be on it's way out. And if it's older than 5 years, then it's warranty is also expired (hence no RMA option). Also, it being one of the cheapest 1.3kW units, doesn't make it too expensive to throw away.
Now, if you'd have 500+ bucks Seasonic unit, then it would be different story. And even then, you could just RMA Seasonic unit since that one comes with 12 years of warranty.

Thank you very much. I don't remember anybody ever giving me this detailed and large amount of useful information on Tom's forum
I come from a place where average salary is 500 dollar so for me 1300R is in the expensive category ;D

I got it without warranty EU import, proxy supplier assumed it was on shells unsold, and ended up in his hands due to them cleaning up the old stock which they often do in EU. Practically throw away good stuff for 1/5 of value to the proxy who isn't very keen on testing.

Got rear ended on last batch bad. So I figured I retrofit this and then some make it into something useful cut part of my losses Very stingy with money since I don't have abundance of it...

I will cut 4 molex modular cables in half making 2 separate 12v lines each carrying 2 Molex so this will give me two MOLEX connectors per 12v wire but both 12v wires will be soldered on same spot (source of power) on HP PSU breakout board and my worry was honestly that I didn't see anybody on internet doing it... Which made me believe that was very dangerous for some unknown factor to me.

Reason I asked about two GND is I have seen a lot of molex to 6pin adapters who use two gnd black wires one from 5v gnd and 12v gnd and one +12v total 3 wires... leading to 6pin gpu adapter end. That made me think perhaps extra ground is for safety? Even tho it's missing 5v wire completely it's a 3pin molex... to 6pin gpu...

 

[Aeacus]

I come from a place where average salary is 500 dollar so for me 1300R is in the expensive category ;D

Why even look towards GPU mining? GPU cryptocurrency mining is dead. Has been for long time.

E.g latest profit chart: https://whattomine.com/gpus?cost=0....profit24_desc&nvidia=true&amd=true&filter=all

Depending on what GPU you have, what the electricity price is and what coin you mine, you either make few cents of profit, taking decades to get even (profit has covered the cost of hardware), or you'll be in the loss for good.

Even when there is no price on electricity, margins are so low that it isn't worth it.

I got it without warranty EU import, proxy supplier assumed it was on shells unsold, and ended up in his hands due to them cleaning up the old stock which they often do in EU. Practically throw away good stuff for 1/5 of value to the proxy who isn't very keen on testing.

PSU that has sit on the shelf for years isn't a "good" PSU to use.

In PSU, there are capacitors. Capacitors age. And in due age, hold less charge, that can lead to all sorts of issues. Like PSU not being able to output the wattage it is rated for. Or PSU struggling to create 5V and 3.3V rails out of the 12V rail. Not to mention that caps that have gone unused for long, can actually explode once fully energized. And when PSU itself is low quality to begin with, all those issues are amplified.

and my worry was honestly that I didn't see anybody on internet doing it...

Well, dabbling around with power delivery, soldering your own connections and the like, hasn't been good idea from the beginning. Now, if you know what you're doing, you can be safe about it. But if you overdo it; ZAP, POOF, magic smoke and maybe even get the Darwin Award.

Better to learn electrical engineering before doing it. Since then, you have the knowledge of the hardware limitations and safety protocols.

Reason I asked about two GND is I have seen a lot of molex to 6pin adapters who use two gnd black wires one from 5v gnd and 12v gnd and one +12v total 3 wires... leading to 6pin gpu adapter end. That made me think perhaps extra ground is for safety?

4-pin MOLEX to 6-pin PCI-E is not a good adapter to use. Since all that does, IF it is 1x MOLEX to 1x PCI-E 6-pin, is taking one wire of 12V and splitting it into 3 wires of 12V. Same with ground, one ground wire is split into 3 ground wires in PCI-E 6-pin connector.

So, while 6-pin PCI-E can sustain up to 216W, 4-pin MOLEX can not sustain that much.
E.g 216W load on 6-pin PCI-E cable means 72W load per one 12V wire. But if you have 4-pin MOLEX coming out of the PSU and then goes to 6-pin PCI-E (via that adapter), then it means the one wire of 12V in 4-pin MOLEX cable has to carry all that load. 216W is too much for 4-pin MOLEX.

Proper 4-pin MOLEX to PCI-E 6-pin have two MOLEX connectors.

Image source: https://www.amazon.com/Cable-Matters-2-Pack-Molex-Inches/dp/B01DV1Z22K

Whereby when you look closely, one MOLEX connector carries 1x 12V and 2x ground, while 2nd MOLEX carries 2x 12V and 1x ground wire. Whereby the idea is, that MOLEX connectors are plugged into separate cables coming from PSU, and not into single cable. Since if it is plugged into single cable, the same 216W per one 12V wire issue comes back.
But having two dedicated MOLEX cables means that one dedicated cable carries 72W and another dedicated cable carries 144W, which falls below 156W limit of MOLEX cable.