Motherboard Thin itx specs confusion

Fireside

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So I've been lurking around this forum for some time, and reading this thread about using a discrete graphics card I had some major questions; please forgive me if these are silly questions. I figured instead of trying to ask there it'd be better to start my own topic.

For starters there is mention that the pcie 4x slot on these thin itx boards is limited to 25 watts. Is this only stated in the manual? I'm not planning a build currently, but this is the board I'm looking at/will be using as a basis for all these questions.
I've looked all over that product page and don't see anything mentioning this limit, or a limit on cpu power usage.

On the thread I linked above, it seemed confirmed that the 2 pin connector (on their board, not necessarily this one) could be used to provide power. Assuming that this were true with my board why couldn't an appropriate adapter be used to hook that directly to a powered pcie riser?
This is coming from my point of view of using a GTX 1050 (non-Ti), which is a card with no extra power consumption needed. I thought that a typical power brick plugged into the board would be enough power for something like that, but I'm unsure and am having trouble finding the information to figure it out. I read mention of an HDPlex, which I'm not entirely sure the function of. Am I right in thinking that it takes in the voltage from the 2 pin connector, and boosts it to something that can be used to power a gpu?

And finally, what on earth is the small board connected to the 24-pin of the HDPlex in post 16 on the above thread?

I really appreciate any help anyone can offer and am sure I'll have more questions as things progress.
 

jeshikat

Jessica. Wayward SFF.n Founder
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The 25W limit is part of the PCIe spec. Only x16 cards are allowed to negotiate the full 75W.
 
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Fireside

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Okay, so then the point of the HDPlex is basically to act as a dc to dc converter? I didn't see where there was a 24 pin plugged into it from a full size PSU, so I don't see how it could be serving any other purpose.
 
Mar 6, 2017
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Yes, it's like an ATX PSU split in two. The AC-DC conversion is done by the external brick, while the DC-DC is done by, in your case, the HDPlex.
 

Fireside

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So in that picture they were using the plex as the psu, supplying voltage via the 2 pin connector, rather than the other way around? That makes a lot more sense if so. In which case the power brick would be plugged into the plex and not into the motherboard itself.
 

aquelito

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The Thin Mini-ITX power issues have been pretty well covered in that thread, as well as by @QinX with two of his builds.

Basically, your board is powered by a 19V AC adapter, while you need 12V for your GPU and powered riser.
The HDPLEX board sole purpose is to provide that 12V voltage.

To provide power to the HDPLEX board, you can use the motherboard 2-Pin connector, used as passthrough output, your AC Adapter being plugged into the motherboard DC connector.

However, for the HDPLEX to start, you need either to jumper its 24-Pin connector (quick solution), or use something like the Add2PSU (what you call the green PCB) or any other circuit to allow the motherboard to start the HDPLEX on startup (elegant solution).

It works great for me :) (case and cable management are temporary).

 
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Josh | NFC

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Is there a powered riser that is easily obtainable that can plug into the DC out on thin-mini? I see step down solutions available but they look jank.
 
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Fireside

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@Josh | NFC I don't think there is simply because the voltage coming out of those 2-pins is 19 volts, not the 12 volts the card would be expecting. So if you were connect them directly without something to step down the voltage you would fry the card.

Thank you so much @aquelito, that description really irons out most of the questions I had. But now I'm curious is there a reason an HDplex (or something similar from the same brand) is used to step down the voltage as opposed to just a plan old d/c to d/c converter that is much cheaper?
 
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Josh | NFC

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@Josh | NFC I don't think there is simply because the voltage coming out of those 2-pins is 19 volts, not the 12 volts the card would be expecting. So if you were connect them directly without something to step down the voltage you would fry the card.

Thank you so much @aquelito, that description really irons out most of the questions I had. But now I'm curious is there a reason an HDplex (or something similar from the same brand) is used to step down the voltage as opposed to just a plan old d/c to d/c converter that is much cheaper?

Right, I totally get that, but I meant something like Qinx's awesome little stepdown board that's attached to the riser assembly. I see more and more pcb powered riser/adapters now so I was just curious.
 

Fireside

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I'm not familiar with said board, so maybe Aquelito can offer some advice.

Also another question for you Aquelito, what are those silver bars going from your cpu to your fan? I understand they are part of the cooling but they look very interesting. I've gone looking around for coolpipes or anything similar (I think thats what you called it in your post) but haven't had any luck finding something.

EDIT: Nevermind, continued looking after I posted that has yielded results. These look fascinating.
 
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aquelito

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@Josh | NFC
Thank you so much @aquelito, that description really irons out most of the questions I had. But now I'm curious is there a reason an HDplex (or something similar from the same brand) is used to step down the voltage as opposed to just a plan old d/c to d/c converter that is much cheaper?

You're welcome.

By DC-DC converter, do you mean something like the one mentioned in this thread ?
I used an HDPLEX 250W board as I already have two of them ! Reliable, well-known solution, with an already made wire harness :)
This way, you can power any GPU up to a R9 Nano, depending on the AC adapter you are using.

However, there is a good news.
As you plan to use a GTX 1050 only, it is possible to get rid of the HDPLEX board and rely on a single 12V brick to power the whole system.
To do so, you need :

- a motherboard that has a wide input DC connector (12V-24V), such as the Gigabyte GA-H110TN. Problem is its DC connector is rated for 10A only, so your only CPU choice is a 35W Intel T CPU.
- a 35W Intel T CPU
- a GTX 1050
- a 10A 12V AC adapter with a 5.5mm DC jack, such as Mini-Box's
- a 4x to 16x powered riser, such a Vary Tech does (website down right now)

To power the riser, you will need a 4-Pin Mini-Fit JR Molex connector to 4-Pin Molex, the motherboard 4-Pin power connector being used as a 12V output.

This is what I plan to do for my next build :)

I've gone looking around for coolpipes or anything similar (I think thats what you called it in your post) but haven't had any luck finding something.

Amec Thermasol Flat Coolpipes. Really great product, much more SFF friendly than usual copper heatpipes.
 
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Fireside

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Sorry for the very delayed response. Been a long few days, and just finished a full day of working on my jeep. Life sucks when you have to mechanic more than work on your pc XD

Anyways, @aquelito correct me if I'm wrong (kinda tired atm, so my thinking may be off) but couldn't you theoretically get a higher ceiling for the cpu depending on the power supply used? Some rough napkin math; assuming I had a 24 volt supply with the boards connector being rated at 10 amps that should give me around 240W in a perfect world. According to the charts here the gpu only uses ~72 watts.

That still leaves 168W for the rest of the system, and at max usage that card only uses 2.9 amps (taken from the same article). I feel like I'm missing something here, considering my card would use even slightly less than the figures shown here.

EDIT: Corrected a few numbers, I shouldn't math when tired.
EDIT2: I read through your post more thoroughly, you're using a 12 volt supply to avoid the need to use a board to step the voltage for the card down to 12 volt. That's exactly what I was missing so nevermind my question XD

Using that supply the math makes more sense at 120W minus the 72W for the card and 35W for the CPU only leaves 13W for ram etc.
 
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