Limitations of external PSUs (eg. Pico PSUs)?

PSUs: The source of DC power for all components in the PC & often a big noise source.

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tbessie
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Limitations of external PSUs (eg. Pico PSUs)?

Post by tbessie » Thu Aug 30, 2018 4:09 pm

Hi folks...

So I want to build a new mini HTPC based on this case:

http://www.atechfabrication.com/product ... Client.htm

I've been having some emails with the owner, and we were talking about power supplies.

I used a wattage calculator to see what would be recommended for the system I want to build, and it suggested 250 watts. I asked the fellow about this, and he said he estimates a 150 watt PSU would be all I really needed, and also that external power bricks aren't available that can do more than 150 watts (or that the cables couldn't carry more than that safely - not sure of the details).

What do you folks think? Have you seen any system where an external PSU is used with a single cable carrying power that supplies more than 150 watts? Is it possible? Or just very difficult to find something that can do that?

- Tim

Abula
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Re: Limitations of external PSUs (eg. Pico PSUs)?

Post by Abula » Thu Aug 30, 2018 8:46 pm

picoPSU 150XT usually gets paired with 150W brick, but there is also a 192W brick more commonly used on 160XT.
What do you folks think? Have you seen any system where an external PSU is used with a single cable carrying power that supplies more than 150 watts? Is it possible? Or just very difficult to find something that can do that?
on RC Car hobby, usually they use 12V-24V PSU to power their chargers, and there are lot higher PSU there, for example Mean Well LRS-350-12 Power Supply, but i kinda think this will defeat the purpose of what you are trying to do, as this are industrial psu, and usually they are very loud. You will also need to do your custom cables and mod the case to pull them in, personally dont think its worth it.

What hardware are you planning on the setup? usually 150W is plenty.

Vicotnik
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Re: Limitations of external PSUs (eg. Pico PSUs)?

Post by Vicotnik » Thu Aug 30, 2018 10:32 pm

tbessie wrote:I asked the fellow about this, and he said he estimates a 150 watt PSU would be all I really needed, and also that external power bricks aren't available that can do more than 150 watts (or that the cables couldn't carry more than that safely - not sure of the details).
I've used the Dell DA-2 brick for high power picoPSU builds in the past. That's a large brick that can deliver 18A@12V. The problem for me building those high power systems has been mainly the power connector. The most common type for low powered systems is a standard barrel DC connector. They are not ideal for a ~150W peak system. My +12V rail was way down, like 11.3-11.4 volts or something and there were stability problems. ;) I did some cable work and replaced the barrel connector with something specified for higher current and after that the +12V rail was fine.

tbessie
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Re: Limitations of external PSUs (eg. Pico PSUs)?

Post by tbessie » Fri Aug 31, 2018 11:43 am

Abula wrote:picoPSU 150XT usually gets paired with 150W brick, but there is also a 192W brick more commonly used on 160XT.

on RC Car hobby, usually they use 12V-24V PSU to power their chargers, and there are lot higher PSU there, for example Mean Well LRS-350-12 Power Supply, but i kinda think this will defeat the purpose of what you are trying to do, as this are industrial psu, and usually they are very loud. You will also need to do your custom cables and mod the case to pull them in, personally dont think its worth it.

What hardware are you planning on the setup? usually 150W is plenty.
Yeah, I want it quiet, so those industrial ones wouldn't be so great. :-/

The plan is this motherboard:

https://www.asrock.com/mb/Intel/Fatal1t ... ing-ITXac/

... with an M.2 main SSD and a couple of high-capacity regular SSDs in there; also, a compact Blu-Ray reader/writer, 16gb or maybe 32gb ram; no other cards (it can take one low-profile card, I think, which I MIGHT put something in at some point in the future).

- Tim

Abula
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Re: Limitations of external PSUs (eg. Pico PSUs)?

Post by Abula » Fri Aug 31, 2018 3:50 pm

tbessie wrote:... with an M.2 main SSD and a couple of high-capacity regular SSDs in there; also, a compact Blu-Ray reader/writer, 16gb or maybe 32gb ram; no other cards (it can take one low-profile card, I think, which I MIGHT put something in at some point in the future).
What CPU? its very likely that you will be fine with 150W, on my 4770K only under prime95 i reached 150W, no other application pushes that setup that high, that with one SSD, a 2.5 laptop drive and 3.5 desktop drive, you can check it on my signature under CAMMI link.
tbessie wrote:The plan is this motherboard:

https://www.asrock.com/mb/Intel/Fatal1t ... ing-ITXac/
That exact motherboard just arrived today =), if you give me some time, i could test it with a i7 8700K, wont be with a picoPSU though, i dont have another 150xt laying around, but it will give you a very good estimate. But not sure i can do it over the weekend, i need to fix my server first, then ill dissaemble the atx setup to grab the 8700k.

tbessie
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Re: Limitations of external PSUs (eg. Pico PSUs)?

Post by tbessie » Fri Aug 31, 2018 5:36 pm

Abula wrote:
tbessie wrote:... with an M.2 main SSD and a couple of high-capacity regular SSDs in there; also, a compact Blu-Ray reader/writer, 16gb or maybe 32gb ram; no other cards (it can take one low-profile card, I think, which I MIGHT put something in at some point in the future).
What CPU? its very likely that you will be fine with 150W, on my 4770K only under prime95 i reached 150W, no other application pushes that setup that high, that with one SSD, a 2.5 laptop drive and 3.5 desktop drive, you can check it on my signature under CAMMI link.
Thanks! The fellow who makes the cases will build whole computers for folks, though I'm going to do most of it myself. He needs the motherboard because he builds in the heat pipes and heat shields himself. I've asked him to install an i7-8700T, which is only 35W TDP. I don't need extreme power, and that chip will, I think, do a fine job for my HTPC needs - what do you think?
tbessie wrote:The plan is this motherboard:
https://www.asrock.com/mb/Intel/Fatal1t ... ing-ITXac/
That exact motherboard just arrived today =), if you give me some time, i could test it with a i7 8700K, wont be with a picoPSU though, i dont have another 150xt laying around, but it will give you a very good estimate. But not sure i can do it over the weekend, i need to fix my server first, then ill dissaemble the atx setup to grab the 8700k.
Ha! Funny that you'd just got the same one! There are similar Gigabyte and Asus ITX motherboards, but the ASROCK has a few more features I wanted (eg. Thunderbolt). I would have preferred to wait until Intel comes out with chipsets that support USB 3.1 Gen 2, Thunderbolt, HDMI 2.0 and DisplayPort 1.4 all natively, but that might be in the next generation or even later, so decided to go with this one. All of the recent computers I've built myself have Gigabyte motherboards, so I'm used to their ecosystem; the last time I built up an Asus motherboard, I didn't like how gamer-focused everything was (the GUI for all of their software looked like it was trying to appeal to 14 year old boys). I'm hoping that ASROCK, given their not-quite-as-mainstream nature, are good.

Let me know what you find out. The 8700K is way much more power than I'll be generating, so if you can use that and it stays below 150w, then I guess I'm safe. :-)

- Tim
Last edited by tbessie on Sat Sep 01, 2018 10:27 am, edited 1 time in total.

CA_Steve
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Re: Limitations of external PSUs (eg. Pico PSUs)?

Post by CA_Steve » Sat Sep 01, 2018 4:17 am

Since the case will support it, go with the vanilla i7 rather than the T part - no upside to the T. The CPU will only draw what power it needs to complete a task. If the CPU horsepower needed is the same or below what the T provides, the power profile between the two parts will be the same. For those tasks (if any - think video transcoding and the like) that require more than what the T part can provide, the job will be done quicker.

tbessie
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Re: Limitations of external PSUs (eg. Pico PSUs)?

Post by tbessie » Sat Sep 01, 2018 10:30 am

CA_Steve wrote:Since the case will support it, go with the vanilla i7 rather than the T part - no upside to the T. The CPU will only draw what power it needs to complete a task. If the CPU horsepower needed is the same or below what the T provides, the power profile between the two parts will be the same. For those tasks (if any - think video transcoding and the like) that require more than what the T part can provide, the job will be done quicker.
Well, my goal was to limit TDP absolutely so that the highest temperature the case will have to deal with will be low, no matter what the load. I suppose I could hobble a full i7-8700 in software (I seem to recall some mobile chips having that feature, not sure about desktop chips) so that the temperatures don't go over a known range, but getting the T-series chip seemed easier. If the chip can never generate more than 35 watts worth of heat, I'd feel more comfortable than if it can do more - the temperature of the entire unit will then stay pretty cool.

You don't see value in that? (not being facetious, actually curious)

- Tim

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Re: Limitations of external PSUs (eg. Pico PSUs)?

Post by CA_Steve » Sat Sep 01, 2018 1:31 pm

Well, my goal was to limit TDP absolutely so that the highest temperature the case will have to deal with will be low, no matter what the load.
What's your horror scenario (application) that would cause this?

The case supports the 95W i7..haven't seen a review or any benchmarks, so I can't say whether it supports it well or not ;) But, the case concept is similar to the HDPlex form factor. So, that raises my expectations and I don't think the 65W i7 will cause any thermal problems. A lot depends on how well the CPU cooler base and heatpipes work. Really, why don't you just ask what temps they saw for the different processors while running their 100% load tests?
Our cooling systems are capable of running a 100% load continuously without throttling the CPU speed.
Could be just under 100C (throttle temp)...could be 50-60C...

Seems a waste to pay the same price and get a nerfed T processor....whether you make use of it's functionality or not.

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Re: Limitations of external PSUs (eg. Pico PSUs)?

Post by CA_Steve » Sat Sep 01, 2018 7:53 pm

Really, why don't you just ask what temps they saw for the different processors while running their 100% load tests?
Just thought of something else - Ideally, they'll have soak test results. So, you can see how temp increases over time with load..and how it drops when unloaded.

Abula
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Re: Limitations of external PSUs (eg. Pico PSUs)?

Post by Abula » Sun Sep 02, 2018 3:07 pm

I just finish the testing, again the build is not complete, Corsair SF600 Platinum is out of stock, but i used a Seasonic Titanium 650 and manage to route the cables where the GPU will be =), single 2.5 SSD, keyboard, mouse and network connected and monitor, nothing on the power saving states, memory running at 3200mhz 1.35V and the 8700K is running at 4.7ghz on load, idle it does drop to 800mhz. As i expected, you should be more than fine with 150W, i only reach that on prime95, and on idle it got really close to what i achieve with the picoPSU 150XT on 4770k and this is with 650W PSU, so you probably will get lower idle than me.
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Re: Limitations of external PSUs (eg. Pico PSUs)?

Post by CA_Steve » Sun Sep 02, 2018 7:28 pm

150W AC...so ~140W DC :)

Nice idle power.

tbessie
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Re: Limitations of external PSUs (eg. Pico PSUs)?

Post by tbessie » Wed Sep 05, 2018 2:08 pm

Thanks for the info, folks! I decided to get a vanilla i7-8700 - that will be way more than I really need for this HTPC, but at least I'll know that if I need more CPU "umph" I can get it (occasional transcoding, etc).

- Tim

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Re: Limitations of external PSUs (eg. Pico PSUs)?

Post by CA_Steve » Wed Sep 05, 2018 5:10 pm

I look forward to a nice user review of the case and build. :)

tbessie
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Re: Limitations of external PSUs (eg. Pico PSUs)?

Post by tbessie » Wed Sep 05, 2018 9:38 pm

CA_Steve wrote:I look forward to a nice user review of the case and build. :)
I'll definitely do that!

- Tim

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