Log Ultimate HTPC: Streacom FC5, BD790i X3D, HD Plex 500W GaN, RTX 5080, Batocera

LukeD

Master of Cramming
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Case Designer
Jun 29, 2016
525
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It's been a while since I last hacked up and crammed something into a case that wasn't supposed to be there.
So here's my latest project, hopefully pulling me back into the scene and inspiring me to complete some of my designs.
Aim here is to build a quiet but very powerful slim HTPC server that will behave like a console with wake on controller functionality, handle multiple emulators with a user (wife/kid) friendly interface.

Components:
Case: Streacom FC5 (silver, no optical drive)
Mobo + CPU: Minisforum BD790i X3D (7945HX3D - 16c/32t)
Memory: Kingston FURY Impact 64GB (2x32GB) 5600MT/s DDR5 CL40 (KF556S40IBK2-64)
GPU: nVidia RTX 5080 Founders Edition GPU
PSU: HDPlex 500W GaN power supply

NOTE: these ram sticks are particularly good for this cpu/mobo combo. Since the max supported speed by the CPU is 5200, the memory down clocks to 5200 but also decreases CL automatically down to CL38. In comparison I also tried the GSkill 5200 CL38 sticks (F5-5200S3838A16GA2-RS) and the system did not want to boot at all.




Seems like everything is going to fit fine. The idea is to cut out vents in the top and bottom panels of the case to allow the GPU to breathe. Air will simply flow from underneath the chassis to the top and hopefully not building up much heat in the chassis itself. As for the CPU/Mobo combo, I'll see if the passive cooling system will be enough for the 16c/32t x3d 7945HX X3D thats in there. The CPU is rated at max 100W TDP while the case passive cooling is design for 95W, so technically with a little tweaking I should be within spec. Otherwise, I'll reinstall the heatsink and 3D print a shroud to direct air over the heatsink and out the back of the case.



POWER:
First thing first I had to figure out if the HD Plex can handle the RTX5080. The HD Plex 500W GaN comes with: 24 pin ATX , 8 pin EPS, 8 pin PCIe (RED), and 4 pin accessory connector.


While the HD Plex can theoretically output 600W burst and 500W sustained, it just isn't cabled up for such a power hungry (350W) gpu as it only has 1 PCIe connector that theoretically can output a safe maximum of 150W (50W per each live wire)
So I had to splice together a custom cable that would tap into the 12v connectors on the PSU.

I used this cable as the basis for rewiring. It's 16AWG which is more than enough to supply the needed 360W. Even an 18AWG cable would have been cable to do this, but the 16AWG gives a little extra piece of mind

... and then created the following custom cable out of it, combining it to an 8 pin EPS cable that was further reduced to 4 pins.


This gave me 6 power lines just for the GPU capable of delivering 50-60w each (300W-360W total)
And what would you know, the GPU is comfortably sipping 355W via the PCIe cable:

I also ran Cinebench since im only supplying this motherboard with 2x50W via the EPS cable and the motherboard/cpu locked in at exactly 100W. In the BIOS there is a setting to set the upper thermal limit. Right now it's at 100W but the PSU managed to cater for the GPU + CPU easily reaching 455W total consumption. The PSU did get hot so I intend to use double sided thermal tape to have the PSU adhere to the front of the case, which is made of a big slab of aluminum. This should also help cool the PSU.
 
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LukeD

Master of Cramming
Original poster
Case Designer
Jun 29, 2016
525
1,337
Placeholder for future updates
 
Last edited:

morj

Airflow Optimizer
Bronze Supporter
Feb 11, 2020
366
698
Great project! Is there any room to route the heatpipes for CPU cooling in the presence of the GPU? I assume they must reach both sides of the case (heatsinks) to grant the full 100W capacity?

Never mind, just read the manual for FC5. The heatpipes are connected only to one side of the case. On the other hand, it's rated for 87W max (and the recommended CPU TDP is 65W).
 

Elaman

Cable-Tie Ninja
Sep 13, 2020
157
119
While the HD Plex can theoretically output 600W burst and 500W sustained, it just isn't cabled up for such a power hungry (350W) gpu
This is brilliant. I wonder what kind of bottleneck / what are we giving up on by using the HTPC board as opposed to a regular desktop CPU/Motherboard ...?
 

LukeD

Master of Cramming
Original poster
Case Designer
Jun 29, 2016
525
1,337
Great project! Is there any room to route the heatpipes for CPU cooling in the presence of the GPU? I assume they must reach both sides of the case (heatsinks) to grant the full 100W capacity?

Never mind, just read the manual for FC5. The heatpipes are connected only to one side of the case. On the other hand, it's rated for 87W max (and the recommended CPU TDP is 65W).
Indeed. With the BD790i X3D I can actually cap the TDP in the BIOS to meet the limitation. But I think ill leave the heatsink on as it is and make a custom fan shroud and potentially use 2 x 92mm fans to suck air from the bottom of the case and push it over the heatsink and out the back of the case. I'll need to cut out two holes on the bottom of the case, which I'm hoping my local machine shop can do it precisely and professionally. Then I'll 3d print a shroud
 

LukeD

Master of Cramming
Original poster
Case Designer
Jun 29, 2016
525
1,337
This is brilliant. I wonder what kind of bottleneck / what are we giving up on by using the HTPC board as opposed to a regular desktop CPU/Motherboard ...?
I'm hoping that the gain is that I have a 16c/32t system within the TDP spec of the case (100W). I'm planning on running a lot of emulators on it like RPCS3, so 32 cores is pretty much a must. It should be much more power efficient than any desktop variant. I was also looking at the Intel 15th Gen Core Ultra 9 285T 1.4GHz 24C/24T but it's only 24T. And that is the T variant (mobile). I want to give the power supply as much surface area of the case as possible to be able to give off heat. I'm worried that if I attach the CPU and PSU to the case for heat transfer, both of them may be too much and it will cook everything inside the case.
 
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