Request details about Molex PCIE risers for mining PSUs on how they handle power "diagrams".
Request details about Molex PCIE risers for mining PSUs on how they handle power "diagrams".
I want to understand whether the molex riser PCIE only draws power from 12V or if both 5V and 12V are needed for proper operation. I’m planning to upgrade a costly Silverstone modular 1300R PSU, which has weakened its 5V compartment but still works well with 12V. The new setup will be a pure 12V 6/8-pin Molex PSU, intended as a secondary power source for a chained dual PSU system used in mining or server applications.
My concern is the 5V pin on the molex riser. Should I use two ground wires for safety, or can a single 2-pin molex work like the one used for fans? Also, can this modification be done on an HP server breakoutboard? It has a 12V and GND area that supplies all power. I’m considering soldering one molex wire to the 12V and another to GND, then using them for PCI risers. Or am I overlooking potential issues like overheating or resistance? Any extra advice would be greatly appreciated. Thanks.
GPU riser cards, whether used in gaming or mining setups, operate exclusively on 12V power. A 5V supply is unnecessary. Riser mounts typically feature two kinds of input connectors: a 4-pin MOLEX (the standard type) and a 6/8-pin PCI-E connector. In the PCI-E version, 5V is not supported at all. That’s a bit of a joke. The Silverstone HELA 1300R is actually one of the most affordable 1.3kW options available. Priced around 280 dollars, it falls far short of the significantly pricier high-end units. For example, similar models can be found here:
https://pcpartpicker.com/products/compar...xr,WrcgXL/
Check out the pricing for Seasonic products. These tend to be more costly, but they represent the best value you can achieve with current technology.
One ground connection is acceptable as long as it doesn’t surpass the 4-pin MOLEX cable’s wattage limit. The second connection is reserved for 5V signals on the same 4-pin MOLEX cable.
If you opt for this configuration, the thin wires in the 2-pin fan cables won’t withstand the power demands. The 2-pin cables usually handle around 30W, which is insufficient for the riser’s needs—typically designed for up to 12W.
Ideally, each riser should have its own 4-pin MOLEX cable. You might manage with two risers per four-pin cable, but if you extend the 4-pin cable further with additional connectors (such as six), you risk damaging it.
A 4-pin MOLEX cable supports up to 156W. A single riser draws about 75W, so you can safely run two risers per cable (total 150W). In theory, each riser should have its own dedicated cable from the PSU.
For example, a dual-PSU 6x GPU mining rig setup:
- Direct link if the image doesn’t load: [link]
I’d recommend considering a new PSU instead, as your HELA R seems to be outdated. If it’s older than five years, the warranty has expired (no return option). Also, given its low price, it’s not worth discarding.
If you’re willing to spend over 500 dollars on a Seasonic unit, the situation changes. Even then, you could return the Seasonic model, as it comes with a 12-year warranty.
I haven't received much detailed and helpful information about Tom's forum before.
In my area, the average salary is around 500 dollars, so a 1300R feels quite high.
I obtained it without any warranty and imported it from the EU. The proxy supplier assumed it was on shells that weren't sold, and it ended up in his hands after they cleaned up old stock in the EU.
They often dispose of good parts at a fraction of their value, which the proxy wasn't interested in testing.
I was hit hard by the last batch, so I decided to modify it and turn it into something useful to reduce my losses.
I'm very cautious with money since I don't have much of it.
I plan to cut 4 molex modular cables in half, creating two separate 12v lines each with two Molex connectors. This way, I'll have two MOLEX connectors per 12v wire, but both wires will be soldered at the same power source location on the HP PSU breakout board.
My concern was that I hadn't seen anyone online doing this before, which made me think it might be risky for some unknown reason.
I asked about adding two GND connections because I've noticed many molex to 6pin adapters using two black wires—one for 5v ground and one for 12v ground, plus a third wire for +12v.
This led me to believe extra grounding might be for safety purposes, even though it completely lacks a 5v wire and is still a 3pin Molex connector for a 6pin GPU adapter.
There are reasons to consider GPU mining, though it's no longer a viable option. The current profit trends indicate it's not worth the effort. For instance, the latest profit data can be found here: https://whattomine.com/gpus?cost=0....pr...filter=all. The earnings depend heavily on the GPU model, electricity rates, and the cryptocurrency being mined. If you have a low-cost power supply and mine certain coins, you might earn just enough to cover expenses, but the returns are minimal or negative over time.
Even without electricity costs, the margins remain extremely thin, making it unprofitable. Old power supplies often have deteriorated components that can fail prematurely, causing performance drops or safety hazards. Capacitors degrade over time, leading to unstable voltage outputs—such as failing to deliver 5V or 3.3V properly. Additionally, a poorly rated power supply can cause overheating or damage.
Experimenting with power systems and DIY connections has proven risky from the start. While some may succeed if they have proper knowledge, others face significant technical and safety challenges. It's generally advisable to invest in more reliable equipment rather than attempting such projects without solid expertise.