Author Topic: Middle of mini-itx build and have power supply vs video card question  (Read 3438 times)

czellmer

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I purchased the XFX R9 285 Video card as recommended and the Silverstone 450W modular power supply as well as the other parts for the $1100 mini-itx gaming build.  I am in the second week of waiting for Amazon to ship the Intel chip after all the other parts arrived a week ago. It is hard not to be able to put it all together, but I digress.

The power supply has only one PCIe output. The card requires 2 six pin PCIe inputs. There is a cable with the power supply that divides the PCIe output into 2 six pin outputs, but the XFX card documentation says specifically to use two separate PCIe power supply outputs. It says using a single PCIe output cable with the 2 six pin inputs is a bad electrical condition and will not supply enough watts to the card.

There are two Y cables shipped with the card that attach 2 four pin Molex connectors normally used as floppy drive into a single six pin PCIe input.  The card has no documentation on these connectors.  From what I can glean from the internet, this is a common last resort way to power a PCIe card requiring six pin inputs. Typically the 12 volt output on the floppy cable is over taxed by the wattage required for the PCI card.  In other words, a bad electrical condition.  The experts I have located online say don't use those y connectors unless you have to do so.

I seem to be stuck between a rock and a hard place.

My full size ATX case and power supply form 5 years ago have two PCIe output cables.  The SFX one from Silverstone only has the one.

I have built my own computers since the 1980's so I do know some about the process.

Do I have to choose from the least worst of the two electrical conditions or is there a solution that I am not seeing?

I am looking forward to getting it all together to have an smaller, quieter, updated, faster, less power hungry computer; but seem to have hit this snag.

Any ideas here?

Ari Altman

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Re: Middle of mini-itx build and have power supply vs video card question
« Reply #1 on: January 20, 2015, 06:31:36 PM »
I purchased the XFX R9 285 Video card as recommended and the Silverstone 450W modular power supply as well as the other parts for the $1100 mini-itx gaming build.  I am in the second week of waiting for Amazon to ship the Intel chip after all the other parts arrived a week ago. It is hard not to be able to put it all together, but I digress.

The power supply has only one PCIe output. The card requires 2 six pin PCIe inputs. There is a cable with the power supply that divides the PCIe output into 2 six pin outputs, but the XFX card documentation says specifically to use two separate PCIe power supply outputs. It says using a single PCIe output cable with the 2 six pin inputs is a bad electrical condition and will not supply enough watts to the card.

There are two Y cables shipped with the card that attach 2 four pin Molex connectors normally used as floppy drive into a single six pin PCIe input.  The card has no documentation on these connectors.  From what I can glean from the internet, this is a common last resort way to power a PCIe card requiring six pin inputs. Typically the 12 volt output on the floppy cable is over taxed by the wattage required for the PCI card.  In other words, a bad electrical condition.  The experts I have located online say don't use those y connectors unless you have to do so.

I seem to be stuck between a rock and a hard place.

My full size ATX case and power supply form 5 years ago have two PCIe output cables.  The SFX one from Silverstone only has the one.

I have built my own computers since the 1980's so I do know some about the process.

Do I have to choose from the least worst of the two electrical conditions or is there a solution that I am not seeing?

I am looking forward to getting it all together to have an smaller, quieter, updated, faster, less power hungry computer; but seem to have hit this snag.

Any ideas here?

Great question, and it's always wise to be cautious in these situations.

The warning from XFX relates to the "average" power supply - XFX doesn't want a user to try powering up a card that requires two PCIe power connections with a sub-par power supply that was truly only designed to provide enough wattage for one PCIe cable. Each 6-pin cable provides 75W, so using two draws 150W - a definite no-no if the power supply doesn't have the capacity for it.

Luckily, you're using the Silverstone 450W model, and Silverstone has designed the unit to be able to supply that extra power, and that's why it includes the splitter cable. They don't have two PCIe cables by default simply to reduce cable clutter with a PSU they know is going into an SFX system (and more likely than not, a Silverstone case).

So rest assured, you'll be fine in this situation using the splitter. The R9 285 is a very efficient card - even with an Intel quad-core CPU, a system using that video card will only draw 200-250W.

Any other questions, just post!

czellmer

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Re: Middle of mini-itx build and have power supply vs video card question
« Reply #2 on: January 28, 2015, 07:26:30 PM »
I finished the build last week and want to thank you for the guide. Everything installed and the computer booted fine. Your parts list and links worked well.

In hindsight I would have done two things differently. I would have spent the extra for the 512 GB SSD you suggested and I would have waited two weeks for the newly released NVIDIA 960 card vs the AMD 285 based card.

What I have works great and will serve me well.

Thanks again.

Clark Zellmer

Ari Altman

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Re: Middle of mini-itx build and have power supply vs video card question
« Reply #3 on: January 29, 2015, 08:03:03 AM »
I finished the build last week and want to thank you for the guide. Everything installed and the computer booted fine. Your parts list and links worked well.

In hindsight I would have done two things differently. I would have spent the extra for the 512 GB SSD you suggested and I would have waited two weeks for the newly released NVIDIA 960 card vs the AMD 285 based card.

What I have works great and will serve me well.

Thanks again.

Clark Zellmer

Clark,

That's great to hear and thanks for the feedback.

The Crucial MX100 512GB SSD option is really a nice one, given its low price. But don't worry, SSD prices will keep dropping, and next year you'll be able to get a 1GB drive for the same price! The beauty of building your own system is that upgrades are easy!

As for the video card, I understand your concern about getting the newest product, but the new GeForce GTX 960, which was released on January 22nd, performs identically to the XFX Radeon R9 285 card you have. It does use less power, but you aren't stressing your system with the R9 285. Given that the cost of the two cards is very similar, it's the closest thing to a tie you'll ever find when a new product is supposed to out-compete an existing product.

By the way, if you'd like to have a profile of your system added to The Gallery on The Tech Buyer's Guru, just send two or three photos of the system along with a few words on the build/use experience to theguru@techbuyersguru.com. I'm sure people would love to see how your mini gaming system came together!
« Last Edit: January 29, 2015, 08:05:08 AM by Ari Altman »