Topic: 2015-2016 LGA1151 (mother board for 6 gpu Rig) Recommendations - page 2. (Read 11624 times)

You actually need zero molex on the mainboard when you have all the cards on molex powered risers (the BIOS will probably demand it anyway and there is no harm in obeying).
It shouldn't be a problem to run 2 cards sitting directly in 16x slots either (if the PSU has decent quality ATX 24-pin wiring/termination and the motherboard was designed for 2+ graphics cards).

On the other hand, I managed to burn two molex/sata cables and a modular socket on a Be Quiet! PSU while running six RX 480 cards on molex powered risers.
Since the PSU had 5 sockets for sata/molex cables (it was actually 6 but I failed to realize that there is an extra, different looking socket, intended for a short molex cable which is there for motherboards with an extra molex but could be used as any standard molex...) and I had 6 cards, I decided to connect 2 cards per cables (6 risers to 3 cables in total).
At first, one of the modular sockets melted a bit with the cable connector getting badly burned in it. (It was still running but I noticed the smell, so turned it off and started investigating.)
Since the other 2 cables looked perfectly fine I thought it was a random fault (either I failed to push it into the socket properly, or the connector was faulty to begin with, etc). I was down to 4 functional sockets in total anyway (well, actually 5, though I believed it's only 4 but it was less than 6 now anyhow), I didn't really have a better choice but to pick another cable and continue to run with 2 risers per cables.
The next time I noticed some smell again, turned it off, and saw as another sata/molex cable (with 2 risers on it) started to burn out. This time, the socket on the PSU remained intact but the cable started to loose it's coating and the SATA plug itself was really hot.

So, these modular sata/molex sockets/cables are clearly not ready to handle this kind of load (2x75W or whatever these cards might eat from the PCI-E slot).
The PCI-E, CPU and most of the ATX 24-pin wires seem to be significantly thicker than these sata/molex wires. The former group of wires go from point-to-point, directly terminated at both ends while the latter ones are "chained" in a way which is (in hindsight) clearly not ready to handle this kind of load (it's basically a single long cable and all the SATA/molex plugs are simply pressed on them, cutting through the insulation and keeping the metallic contact thorough "pressured razor blade" kind of fashion).
It's also notable that the extra short molex, intended for direct motherboard connection, is also point-to-point, directly terminated at both ends (not a razor blade pressured and chain-able kind like all the rest).

The TL;DR lesson is that even though the ATX 24-pin connector/cable clearly has it's own limits, the sata/molex cables intended for hard/optical drives can be significantly weaker.

I recently replaced that PSU and wired the new one with 1 card per molex/sata cable from the beginning (it has 6 identical sockets for these kind of cables). I will probably use the slightly damaged PSU with 3 or 4 cards at max later on (when I will have some fresh mining profit to reinvest).

I like the Asrock motherboard with the  2x 4pin molexes in the board to give extra power. that is much safer.

I wonder if anybody tried the workstation counterparts of the B150 and H170, namely and respectively the C232 and C236 chipset based boards (these are probably the exact same silicon but with microcode support enabled for some entry level E3V5 Xeon CPUs and ECC memory [when the Xeon or Pentium/Core CPU also supports ECC] on top of the "lesser" consumer CPU and memory parts).

These boards aren't exactly cheap in general (but neither too expensive compared to some of the "fancier" consumer parts, especially if they live up to their promise of being more stable and reliable than their consumer counterparts) and I am yet to see any SKU with >5 PCI-E slots (they might restrict the numbers on these boards for an inherent reason rather than wiring up countless slots regardless if they will work or not ) but they might worth a closer look and try (search for a relatively cheap one with >4 slots, =6 if any and give it a try...).

Asrock has made the decision to stop manufacturing both the Pro BTC and the H97 Anniversary.  The reason I was given was slow sales.  They will do a special run of the mobos if you have a large enough order.  I would expect the order to have to be a few $100k.
 

With this board you need powered risers. The asrock btc boards have 2x 4pin molexes in the board to give extra power.

I must agree too Z170 chipset is having problem with 3+ cards on most boards, its prolly bios related, but who ever is doing testing first disable all non needed IO and internal devices as:
- sound
- ports
- any add in hw as firewire, wifi, etc
- set PCI-e to x1 mode if possible

And only then test it, also better use win10 because it should handle 8 GPU with no moded drivers

Thats why I posted links to other chipsets, the Z170 chipset will only handle 3 or 4 cards depending on the board. OP stated "maybe a socket 1151  mobo."

The boards mentioned above below are not LGA1151, of which the OP is ask.

The consensus that I've read in these threads is that the Z170 chipset does not handle more than 4 cards very reliably/at all.

https://www.aliexpress.com/item/90-for-new-Original-for-Biostar-H61B-H61-LGA-1155-DDR3-16G/32723336716.html

https://www.aliexpress.com/item/PC-computer-motherboards-BIOSTAR-TB85-ETH-LGA-1150-Intel-Core-i7-i5-i3-Xeon-Pentium-DDR3/32677397969.html

I tried an ASUS H170 Gaming board and only 3/6 slots worked.
4/6 was possible depending on the right slot assignment and UEFI Setup configuration but it wasn't really stable under mining load for longer periods.
5/6 was a disaster: the misbehaving SATA controller caused data corruption on the root filesystem up to the point where Windows became unbootable.
6/6 was better, it didn't even get through the firmware initialization, so it had no chance of corrupting data on the SATA drive.

I took it back to the store and left with a 6-slot Gigabyte Z97 Gaming 3 (v1.1) because they had one of those at stock. It works great so far (and it looks like a decent PC mainboard unlike those 80/90-series 6-slot Asrock boards, so it might be easier to sell when the time comes...).

what windows version are you using with your MSI Z170-A Pro setup ?

Hi, I have some experience building 6 gpu mining rigs, the mobo of choice use to be the Asrock h80 btc pro or the h97 Anniversary. As most of miners know, those boards are disappearing from the market, I don't even know  if it is a low stock issue which would be temporary, or if Asrock stopped their production.

Right now Im looking for a replacement, maybe a socket 1151  mobo, that is able to handle 6 gpu. I have an MSI Z170-A Pro. The board has enough PCIe to connect the 6 gpus, but with only 5 the system becomes highly unstable, and with 6 its a constant reboot festival.

So my question is, which modern Mother board that is still in production, and is proven to be able to handle 6 gpus  do you recommend? or  maybe any of you were able to run a 6 gpu rig using a 1151 Motherboard (z170 chipset) and you could share how you manage to do it?

Thank you in advance for taking the time to read and answer to this.