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idodos · 2013-03-27, 18:31

Hello dear xbmc community!
I have recently started ordering parts for a thin itx htpc build and am having second thoughts about my power supply of choice.
The specs are as follows:

Intel Desktop Board DQ77KB
Intel Active Thermal Solution HTS 1155LP
i3-3225 Dual core CPU
Crucial m4 128ga
4gb ram of some brand

So back to my question, should I buy a 120w psu or will a 90w do?
And if a 90w is enough, is there any form of advantage to getting a 120w psu seeing as the price is not at all much higher?

Thanks in advance!

**Dougie Fresh** · (This post was last modified: 2013-03-27, 18:35 by Dougie Fresh.)

The DQ77KB has a DC-DC power supply built into it so all you need is an AC adapter, no picoPSU or regular power supply is needed. The AC adapter should be 19V and have a 7.4mm * 5.0mm tip. It plugs right into the back of the motherboard.

This is the one I use for thin mini-ITX builds: Anker 19V 4.74A 90W AC adapter

idodos · 2013-03-27, 21:55

(2013-03-27, 18:34)Dougie Fresh Wrote: The DQ77KB has a DC-DC power supply built into it so all you need is an AC adapter, no picoPSU or regular power supply is needed. The AC adapter should be 19V and have a 7.4mm * 5.0mm tip. It plugs right into the back of the motherboard.

This is the one I use for thin mini-ITX builds: Anker 19V 4.74A 90W AC adapter

Thanks for replying!
I was actually talking about ac adapters, perhaps I should have mentioned lol
So just to make it clear, there is no reason to use a 120w adapter?
As the price is not much higher?

voochi · (This post was last modified: 2013-03-27, 22:06 by voochi.)

90W brick is fine for i3.

120W will just run cooler and allow you to use it with something more powerful in the future. But if that is not a concern then it is irrelevant.

Of course, if the price is nearly the same then you may as well get 120W just for the sake of it.

**Dougie Fresh** · 2013-03-27, 23:21

Just make sure it's 19V with a 7.4mm * 5.0mm tip. AC adapters used for picoPSUs will not fit the DQ77KB.

Some of the Intel literature on the DQ77KB has the wrong size plug quoted as 5.5mm * 2.5mm which is wrong -- that's for the DN2800MT thin mini-ITX motherboard.

idodos · 2013-03-28, 00:53

(2013-03-27, 22:05)voochi Wrote: 90W brick is fine for i3.

120W will just run cooler and allow you to use it with something more powerful in the future. But if that is not a concern then it is irrelevant.

Of course, if the price is nearly the same then you may as well get 120W just for the sake of it.

Got it, well guess I'll just go for the 120, thanks!

joe7dust · (This post was last modified: 2013-03-28, 11:49 by joe7dust.)

(2013-03-27, 22:05)voochi Wrote: 90W brick is fine for i3.

120W will just run cooler and allow you to use it with something more powerful in the future. But if that is not a concern then it is irrelevant.

Of course, if the price is nearly the same then you may as well get 120W just for the sake of it.

Would you mind explaining how a 120W adapter is going to make this rig "run cooler" compared to a 90W one? I've been building PCs for years and never heard of this. If anything the adapter itself will general more thermal waste (heat) as it is actually drawing more power through it. Not to mention it should result in a slightly higher electric bill.

idodos · 2013-03-28, 12:01

(2013-03-28, 11:48)joe7dust Wrote:
(2013-03-27, 22:05)voochi Wrote: 90W brick is fine for i3.

120W will just run cooler and allow you to use it with something more powerful in the future. But if that is not a concern then it is irrelevant.

Of course, if the price is nearly the same then you may as well get 120W just for the sake of it.

Would you mind explaining how a 120W adapter is going to make this rig "run cooler" compared to a 90W one? I've been building PCs for years and never heard of this. If anything the adapter itself will general more thermal waste (heat) as it is actually drawing more power through it. Not to mention it should result in a slightly higher electric bill.

I believe that he meant that the ac adapter will run cooler. It shouldn't draw much more power if the board doesn't require it, but that's just a thought so I could very well be wrong.

joe7dust · 2013-03-28, 12:12

(2013-03-28, 12:01)idodos Wrote:
(2013-03-28, 11:48)joe7dust Wrote:
(2013-03-27, 22:05)voochi Wrote: 90W brick is fine for i3.

120W will just run cooler and allow you to use it with something more powerful in the future. But if that is not a concern then it is irrelevant.

Of course, if the price is nearly the same then you may as well get 120W just for the sake of it.

Would you mind explaining how a 120W adapter is going to make this rig "run cooler" compared to a 90W one? I've been building PCs for years and never heard of this. If anything the adapter itself will general more thermal waste (heat) as it is actually drawing more power through it. Not to mention it should result in a slightly higher electric bill.

I believe that he meant that the ac adapter will run cooler. It shouldn't draw much more power if the board doesn't require it, but that's just a thought so I could very well be wrong.

Even if that is what he meant I am still confused. As I said it should general MORE thermal waste not less, as it COULD draw more power. If it doesn't draw any extra power, that means it will run at the same temp, never cooler.

idodos · 2013-03-28, 13:06

(2013-03-28, 12:12)joe7dust Wrote:
(2013-03-28, 12:01)idodos Wrote:
(2013-03-28, 11:48)joe7dust Wrote: Would you mind explaining how a 120W adapter is going to make this rig "run cooler" compared to a 90W one? I've been building PCs for years and never heard of this. If anything the adapter itself will general more thermal waste (heat) as it is actually drawing more power through it. Not to mention it should result in a slightly higher electric bill.

I believe that he meant that the ac adapter will run cooler. It shouldn't draw much more power if the board doesn't require it, but that's just a thought so I could very well be wrong.

Even if that is what he meant I am still confused. As I said it should general MORE thermal waste not less, as it COULD draw more power. If it doesn't draw any extra power, that means it will run at the same temp, never cooler.

But if the same power is drawn, and is spread across a larger surface, shouldn't that, in fact, generate less heat?

voochi · (This post was last modified: 2013-03-28, 15:49 by voochi.)

(2013-03-28, 11:48)joe7dust Wrote: Would you mind explaining how a 120W adapter is going to make this rig "run cooler" compared to a 90W one? I've been building PCs for years and never heard of this. If anything the adapter itself will general more thermal waste (heat) as it is actually drawing more power through it. Not to mention it should result in a slightly higher electric bill.

The 'rig' will not run cooler. We are talking about the external power brick.

A 6A power brick can quite simply handle more current than a 5A one. They are rated according to their ability to handle current. The failure mode when you draw more current than a power brick can handle is typically that it overheats (and hopefully blows an internal fuse or triggers some other protection).

Therefore it is very simple, under equal load a 120W brick runs cooler than a 90W brick, is further away from its current limit. It is simply an extra margin of comfort/safety and hopefully will last longer.

**Dougie Fresh** · (This post was last modified: 2013-03-28, 15:35 by Dougie Fresh.)

This rig will see 30W-40W consumption during normal usage with a maximum draw under 80W so given the 50% rule, the 90W will be more efficient than the 120W.

The thermal characteristics of a AC adapter brick have more to do with the efficiency and quality not the wattage rating. It's the inefficiency in the AC-to-DC conversion that creates heat. The more inefficient the process, the more heat. That's why I stick with the Anker brand -- I've found them to run cool and to be better quality than some of the cheaper aftermarket AC adapters.

I am not sure 90W or 120W is going to make a big enough difference here though to care.

joe7dust · 2013-03-28, 15:55

Did my last post get deleted? I thought I replied already but apparently it didn't work or was deleted. Since I've received no message from a moderator I shall assume it was an error on my end...

To answer the OP's last question... No! It will not generate less heat. It may feel cooler to the touch IF* it radiates from a larger surface area, but the total heat output should not go down when moving to a higher wattage. If anything it could go up.

*I say IF because I doubt the 90w and 120w outer plastic shells are even different sizes.

awp0 · 2013-03-28, 17:18

Honestly if the only hard drive that you have is that single SSD then you could run this thing on a 60w adapter. That said, the difference in efficiency between these adapters is pretty small, so I would probably just go with a larger one so that you can add drives (or whatever) later.

bluray · 2013-03-28, 19:34

When comparing the power brick, it is not exactly the same as the standard ATX PSU. If you are talking about efficiency of the 90W brick vs. 120W brick, the 120W brick have a slight edge in efficiency rating. We asked one of the tech to do some tests on the power bricks in similar power ranges for several laptops at work several years ago. Since the 19V AC-DC power adapter operates at very high efficiency, I highly doubt that you find much of a different between them on Intel DQ77KB/i3-3225 HTPC. If the price is not very much different, I would go for the 120W brick. If nothing at all, the 120W will give you some head room for future upgrades too.....

Mini-box supplied even bigger brick for Intel DQ77KB on their website- DQ77KB Intel Mini-ITX....