Question Motherboard to PSU connection questions: An ASUS Z170-WS "Workstation" Motherboard and its "EATX . . . " connections

[BonzaiDuck]

Here is page 1-32 of my ASUS Z170-WS motherboard manual:


I'm not sure, but I don't think I've ever worked with a motherboard in the EATX spec. This motherboard is an ATX motherboard in its size spec. It requires, in addition to the 24-pin EATXPWR connection plug, two 8-pin EATX12V connections with plugs sitting side by side, and a third EATX12V connection to a plug with six pins. No information in the manual explains any circumstance where one would not connect all of these plugs, so one assumes they all require connections to the PSU.

I have a Seasonic Prime Titanium TX-750 750W PSU, and I assume that it at least meets the ATX 2.0 specification because the spec is long-established and most PSUs comply with it and with later versions.

So, in addition to the cable and PSU ports for the 24-pin connector, I have two 12V 8-pin "CPU to PSU" cables, which will fill the bill for connecting EATX12V and EATX12V1 as shown on the mobo manual page. This leaves a need for a cable connecting the 6-pin EATX12V_1 plug to the PSU. The only cables available other than SATA and legacy 4-pin Molex connectors are the PCI-E-to-PSU cables. We always use these for graphics card power connections. They are capable of fitting an 8-pin plug on a PCIE device, but two of the pinouts are separable and are not used in graphics cards I've had, leaving the use of the main six-pin connector.

SHOULD I ASSUME that it is this type of PSU-to-PCIE cable intended to fit the third motherboard power plug (EATX12V_1)? I notice that all of the molded retainers of the pins fit the pattern or shapes of the corresponding pinouts on the motherboard plug, except one. On the left side of the motherboard plug's diagram, the middle pin-out is square, while the Seasonic PCIE cable has a rounded edge for the corresponding pin. Thus, the cable will still fit the motherboard plug. One might describe it this way: you can put a round peg in the square hole, but you cannot put a square peg in a round hole

I don't want to connect my Titanium PSU and high-end workstation motherboard in any way that will fail their functions or cause damage to either one.

I know this nit-picky concern might seem silly or trivial to some, but some people may have more experience with this type of workstation motherboard and its 12V connections, so someone would know for sure. That's better than my making educated guesses, with a lack of experience for this type of motherboard.

Thank you very much for your comments and guidance.

 

[zir_blazer]

EATX is pretty much a Motherboard size, it doesn't need specific power connectors as far that I know.

I think there was a discussion about those Motherboards with multiple EPS12V inputs (Or ATX12V 8 Pins, whatever you like to call them). On Multiprocessor platforms typically it is one dedicated for each Processor. Some overclocking Motherboards supports two for a single one like yours do, but it is completely overkill if you're not doing some extreme overclocking, cause each EPS12V was capable of around 250W-300W or so, don't remember exactly. Some Motherboards may however not want to boot if they aren't fully populated (One is mandatory for obvious reasons), albeit that depends on the Motherboard itself.
The other near the slots is effectively a PCIe 6 Pins power like the one used for Video Cards. It is used as 12V 75W reinforcement for the PCIe Slots since the standard ATX 24 Pins only has two wires for 12V, and a Motherboard with 3 16x slots is borderline capable of overloading them (Each 16x PCIe Slot can provide up to 75W for cards, so you have 225W there). Yours have 4 slots. I don't know whenever it is mandatory to populate it, but you want to do so if you have more than 2 16x cards.

 

[BonzaiDuck]

EATX is pretty much a Motherboard size, it doesn't need specific power connectors as far that I know.

I think there was a discussion about those Motherboards with multiple EPS12V inputs (Or ATX12V 8 Pins, whatever you like to call them). On Multiprocessor platforms typically it is one dedicated for each Processor. Some overclocking Motherboards supports two for a single one like yours do, but it is completely overkill if you're not doing some extreme overclocking, cause each EPS12V was capable of around 250W-300W or so, don't remember exactly. Some Motherboards may however not want to boot if they aren't fully populated (One is mandatory for obvious reasons), albeit that depends on the Motherboard itself.
The other near the slots is effectively a PCIe 6 Pins power like the one used for Video Cards. It is used as 12V 75W reinforcement for the PCIe Slots since the standard ATX 24 Pins only has two wires for 12V, and a Motherboard with 3 16x slots is borderline capable of overloading them (Each 16x PCIe Slot can provide up to 75W for cards, so you have 225W there). Yours have 4 slots. I don't know whenever it is mandatory to populate it, but you want to do so if you have more than 2 16x cards.

That was my understanding, that EATX was primarily a size spec for extra board width. But then you would figure that a full-size EATX board would more likely use the extra power connections.

I picked up this board in a panic-buying episode toward repairing and upgrading my Sabertooth Z170S. The Sabertooth only has a certain number of PCIE lanes. It will allow SLI such that the two cards are running as x8. The remaining full-size PCIE slot is full x16 in size but only works at a maximum x4. The NVME M.2 connector may share bandwidth with other drive connections to the SATA controller, but is given priority by the hardware.

The workstation board, on the other hand, may have more than dozen (or two? gotta-look-it-up) extra PCIE lanes and apparently the ability to run 3x x16. The extra PCIE lanes work through a bridge chip.

What am I GOING to USE them for? I'll put an NVME M.2 in one of the two motherboard slots -- the one that shares bandwidth with a U2 connection, which I'm not using. As far as I know, the NVME will still be "almost" limited for communicating with the CPU via 4 DMI lanes. So I'll put another NVME M.2 in the bottom x4 PCIE slot -- for starters. I"ll put another smaller NVME in one of the x16 slots. So that's two x4 cards. I may even add a "nothing special" Marvell SATA/RAID controller card in another slot, and I think this controller is an x2 PCIE card. Of course, one of the top PCIE slots will go to (something like) a GTX 1070. In the Sabertooth, the GTX 1070 runs at x8 for having other slots occupied. In the workstation board, it will run at x16. I really don't expect a lot of difference with that, but it's as good as a GTX 1070 can get -- when you can find a 1070, 2070 or 3070 to get in the first place. Worse -- because even if some were available, I'd only want a "Mini" OC card.

SO! Would you say I should connect the PCIE to PSU connector to the 6-pin plug? Or just leave it vacant? Because if it's a matter of supplying an extra 75 W, I'm not sure it will need it. What do you think? Is it a choice for which you would say "It wouldn't hurt, but it probably doesn't matter"?