The smallest possible case? (Using "normal" components+layout)

Dyson Poindexter

If there's empty space, it's too big!
Original poster
Jun 25, 2015
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We all want small cases. What I want to know is, is it possible to make a case that is 100% constrained by the dimensions of its components?

The requirements are:
  1. Mini ITX board
  2. Front-PSU shoebox form factor (Xigmatek Eris or HAF Stacker 915F layout)
  3. Use a full-height single slot GPU inserted directly into the PCIe slot (no risers)
  4. Use an internal SFX psu (no dc-dc with external bricks)
  5. Rectangular prism profile (no cylindrical or pyramid cases)
  6. Width must be no wider than that of a Mini ITX board (~170mm)
  7. Height must be no taller than the top of the PCIe card (~110mm)
  8. Depth must be no deeper than the motherboard + SFX PSU (~170+100mm)
Here's a quick render. Orange is the motherboard, red is GPU, purple is PSU.



We can also barely squeeze a 240mm radiator up top if we really try:



Using a short GPU (R9 Nano) and putting the PSU above the motherboard, we can converge upon the truly smallest possible case for these constraints. A tad over 3 liters in volume. Mathematically as small as possible.




Can such cases be made? Is it possible in the real world? Using a single slot for a high-end GPU means watercooling is mandatory.

I've long dreamed for a case like the render with a radiator, but the tubing would have to exit out the back of the card (Like an R9 Fury X). That would mean a custom machined waterblock or modded AIO. The CPU cooling would probably be an AIO as well, no reservoir either. Two AIOs modded together Not easy. But, I think it is possible.

Here's the OpenSCAD markup if someone wants to play with it:

Code:
group(){//2x120mm rad with fans
color ("white")
translate([-110,5,80]){   
cube([279,124,30],false);   //based on alphacool st30
}
color("green")
translate([20,7,65])
cube([120,120,15],false);
}


group(){//SFX psu
color ("purple")
translate([-105,5,0]){   
cube([100,125,64],false);   //numbers from Silverstone
}
}


group(){//pcie card
color ("brown")
translate([-80,155,8]){   
cube([250,15,100],false);   //generic 250mm GPU
}
}


group(){//mini itx board
color("orange"){   

translate([60,60,5]){   
cube([60,60,20],false);   //cpu/waterblock
}

translate([30,155,5]){   
cube([130,8,10],false);   //pcie slot
}

translate([150,0,5]){   
cube([20,150,40],false);  //IO area
}


cube([170,170,5],false);  //board
}
}
 

jeshikat

Jessica. Wayward SFF.n Founder
Silver Supporter
Feb 22, 2015
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What I want to know is, is it possible to make a case that is 100% constrained by the dimensions of its components?

It's really difficult, especially with metal cases. Once you account for bend radius, minimum flange length, minimum feature/hole/cutout/etc to edge distance, access for tooling, tolerance for manufacturing variance, room for assembly, clearance between parts so they don't short out on something, and so on, you gain bits of space here and there.

For example, the Mini-ITX motherboard spec says there should be at least 6.35mm from the bottom plane of the motherboard to the chassis. That space is used to make sure nothing shorts out, M.2 connectors, heatsink backplates, etc.

If you want to keep the IO shield then it extends a bit past the top edge of the board.

You'll want a little bit of space between the front edge of the board and the PSU/chassis to plug/unplug the 24-pin.

This is why so many indie case designs gain a liter or two or three over the course of development.
 
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Dyson Poindexter

If there's empty space, it's too big!
Original poster
Jun 25, 2015
55
62
Great points! There would definitely need to be some keepout and case material factored into it. There's also constraints based on the components used. It would be more of a one-off. If I were to make one, I'd use some think steel sheeting welded/brazed on 5 sides, and probably a "lid" that screws on the top, if I could get tabs to fold in. It would be a pain to build inside, but once done would be the most perfect case, if perfection is defined by volume.

Also, I'd likely mod the SFF PSU to have the AC input on the same side of the DC outputs. So not 100% stock but still easy to do.
 

jeshikat

Jessica. Wayward SFF.n Founder
Silver Supporter
Feb 22, 2015
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It would be a pain to build inside

Yup :p

Also, I'd likely mod the SFF PSU to have the AC input on the same side of the DC outputs. So not 100% stock but still easy to do.

I wouldn't say that will be easy. The modular connector daughterboard will be in the way on modular units. It could maybe work with something like the ST30SF.

HDPLEX is working on a 250W version of this: http://www.hd-plex.com/HDPLEX-Internal-160W-AC-DC-Adapter-with-Active-PFC-and-19VDC-Output.html

I think length and width will be the same, but height will increase to 52mm.

So that in combination with their 250W DC-ATX unit could be a good alternative to a SFX unit.
 

hardcore_gamer

electronbender
Aug 10, 2016
151
125
Interesting concepts,
Doing a quick math: your first design will be at least 120 x 170 x 295mm (6L) theoretically .
GPU height x Mini ITX width x (Mini ITX length + SFX length, Also 295 would fit most GPUs.)

A real design taking in the factors @Aibohphobia mentioned would be close to 7L. Here are a couple of 7L cases that support mini ITX, SFX PSU and a full size GPU :

1. Zaber sentry 66 x 310 x 340mm (7L)
2. Dan A4 SFX 112 x 200 x 317mm (7.1L)

Second design would be at least 120x170x170mm (3.5L) in theory. Again a practical design may exceed 4L.
 
Last edited:

CC Ricers

Shrink Ray Wielder
Bronze Supporter
Nov 1, 2015
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Zaber's Sentry is closest to the size of the Steam Machine's console form factor. But both the Sentry and A4 break Poindexter's rule 3: the provision of needing a PCIe riser.

If we were to go completely riser-free, I'd say we can still do 7L but it will be restricted to short ITX sized graphics cards (or less than 200mm at the most). It would have a layout like the Osmi. If you want to support cards at least 270mm long, it will start to resemble the Ncase M1 in layout. But get rid of the 3rd slot (what cards need those nowadays) and you can easily get it under 12L in size.

Limiting it to just a single slot card for water cooling is an interesting consideration. But dammit NVidia, you guys still make reference cards with a superfluous DVI port for the 2nd slot. Either we'll have to go AMD only with the graphics card, or have some cojones and chop the extra DVI slot voiding the warranty.
 

hardcore_gamer

electronbender
Aug 10, 2016
151
125
Zaber's Sentry is closest to the size of the Steam Machine's console form factor. But both the Sentry and A4 break Poindexter's rule 3: the provision of needing a PCIe riser.

If we were to go completely riser-free, I'd say we can still do 7L but it will be restricted to short ITX sized graphics cards (or less than 200mm at the most). It would have a layout like the Osmi. If you want to support cards at least 270mm long, it will start to resemble the Ncase M1 in layout. But get rid of the 3rd slot (what cards need those nowadays) and you can easily get it under 12L in size.

Limiting it to just a single slot card for water cooling is an interesting consideration. But dammit NVidia, you guys still make reference cards with a superfluous DVI port for the 2nd slot. Either we'll have to go AMD only with the graphics card, or have some cojones and chop the extra DVI slot voiding the warranty.

I know that many people hate PCIe risers / extender cables. However, in practice, well made riser/extender cables have almost no noticeable performance impact , especially for the short ones that Zaber Sentry use.

For a 7L case, full size card + riser is a much better option than iTX card with no riser.
 

Thehack

Spatial Philosopher
Creator
Mar 6, 2016
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I know that many people hate PCIe risers / extender cables. However, in practice, well made riser/extender cables have almost no noticeable performance impact , especially for the short ones that Zaber Sentry use.

For a 7L case, full size card + riser is a much better option than iTX card with no riser.

That is true, but for small niche case the riser adds a huge cost.

I have also crunched the numbers and the smallest you can go is around 6L if you limit hardware options a lot. 140mm x 210mm x 180mm should be your internal space. But this leaves little to no room for the cpu cooler or place to put cables. Realistically 6.5L to 7.5L is your sweet spot for compatibility.

Picobox is also working on a 250W pico PSU that supports a 6 pin pcie.
 

hardcore_gamer

electronbender
Aug 10, 2016
151
125
That is true, but for small niche case the riser adds a huge cost.

I have also crunched the numbers and the smallest you can go is around 6L if you limit hardware options a lot. 140mm x 210mm x 180mm should be your internal space. But this leaves little to no room for the cpu cooler or place to put cables. Realistically 6.5L to 7.5L is your sweet spot for compatibility.

Picobox is also working on a 250W pico PSU that supports a 6 pin pcie.

Agreed. Around 7L is where the sweet spot is for full size GPU+ SFX/SFX-L PSU. I'd say Zaber sentry is one of the best implementations of this volume in terms of space efficiency, aspect ratio, and aesthetics. There's pretty much nothing left to shave off and assembly / cable management is way better than DAN A4 SFX.

That being said, if you're willing to use Flex ATX PSU and Mini ITX GPU, the sweet spot shifts to 4 to 5L. Two best examples can be found here:
1. Hutzy XS @3.99L
2. Freilite Brevis S larger at @4.957L, but slimmer design

Sub 3 - 3.5 L designs require HDPLEX/Pico PSU + external power brick.
 

Dyson Poindexter

If there's empty space, it's too big!
Original poster
Jun 25, 2015
55
62
Risers do help out a lot with packaging when you can place the GPU over the motherboard, but I've never liked the requirement to use a really thin heatsink on the CPU. Additionally, the layout kinda precludes any watercooling. If the GPU could be turned to face the CPU, (a la Project Quantum) I think the common heatsink would have some advantages. Riser builds with the GPU folded away from the motherboard always end up looking like the shape of a VCR which is a massive turnoff for me. I like small cubes!

While a SFX PSU might fit in the area between a vertical GPU and the ITX board, I think it's not very realistic. But, it's a goal to converge on! It looks like the PSU would be right up against the IO bracket, so any cooler that works in an M350 would probably be usable. Then you'd have to worry about the GPU...

 

hardcore_gamer

electronbender
Aug 10, 2016
151
125
Here are my renderings with an Asus 970 Direct CU Mini and Silverstone SFX-L:
(Power supply is in an inverted configuration to avoid PSU fan and CPU fan inhaling from the same area and in opposite directions.











Dimension of the setup: 198 x 136 x 170mm. This may fit in a 210 x 150 x 190mm (5.9L) case. CPU cooling could be an issue tho. It is blocked at 3 horizontal directions by I/O shield, GPU and RAM.
 

Dyson Poindexter

If there's empty space, it's too big!
Original poster
Jun 25, 2015
55
62
That's close to it! I'd mod the 970 to have the power connector on the back of the PCB, then flip the PSU over and let its fan cool the CPU.

It might be an oven, but it would be tiny!
 

hardcore_gamer

electronbender
Aug 10, 2016
151
125
That's close to it! I'd mod the 970 to have the power connector on the back of the PCB, then flip the PSU over and let its fan cool the CPU.

It might be an oven, but it would be tiny!

That may not work. PSU fans intake air towards the inside of the PSU. SFF CPU fans blow air down towards the CPU. That's why I kept the PSU in the inverted configuration. Also, even if you lower the PSU so that it touches the I/O shield, you'll have enough space to put a low profile cooler like Noctua NH-9i on the CPU.

I recommend gtx 1060 and gtx 1070 mini ITX cards as they're more powerful than previous generation cards of the same size and power consumption.

I'd also suggest looking at Flex ATX PSU options. It may give more room for the CPU to breath, at the expense of increased noise due to small PSU fan.
 

Dyson Poindexter

If there's empty space, it's too big!
Original poster
Jun 25, 2015
55
62
You don't have to have a CPU fan blow down, though. Yes, it might not be as efficient as a "push" fan, but having a CPU heatsink with a "pull-pull" fan setup using the cooler's fan and the PSU's fan should generate great airflow. Vent the case such that air comes in from the side opposite the PCIe slot, and you would have great VRM cooling, and very good fresh air access to the CPU.

Has anyone here done custom heatpipes? Having a heatsink on the GPU where heatpipes swing around to the back of the card would be interesting....
 

Dyson Poindexter

If there's empty space, it's too big!
Original poster
Jun 25, 2015
55
62
I know it's wildly impractical, but having a unified heatsink might let the envelope be pushed a little more. I recall the old 775 boards with their extravagant heatpipe arrangements.



Sharing the thermal load between CPU and GPU would allow the system to work better in situations where the loading may be uneven. In gaming, you might have a GPU using 80% of the thermal solution's capacity while the CPU only needs 20%. Project Quantum is a neat solution, but the cabling situation is a mess with the GPU in there backwards. An "inverted GPU" would be the ideal choice, then the CPU and GPU could be cooled with an L-shaped heatsink. Better yet, an ITX board with the PCIe slot at the top. No funky GPU needed.
 
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CC Ricers

Shrink Ray Wielder
Bronze Supporter
Nov 1, 2015
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Some might be interested in this layout I thought up a while ago:



It came about from the question "how can I make the Osmi case better?" So I thought up a similar case layout where you can fit a 120mm or 140mm AIO liquid cooler on the top, which would be a good work-around for the low clearance space for the CPU area immediately beside the PSU. Prop up the case with feet, and a ITX graphics card can get air from bottom vents.

The above image is to scale. 20 pixels equals 10mm.
 

iFreilicht

FlexATX Authority
Feb 28, 2015
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pull-pull" fan setup using the cooler's fan and the PSU's fan should generate great airflow.

I wouldn't put two fans right next to each other. That has no benefit whatsoever, airflow doesn't increase, and you'll generate and incredible amount of turbulence, so it will be noisy as well. What you could do is use a fan like the Scythe Kodati, where the fan is underneath the heatsink, to get a push-pull configuration like some have on their radiators. That could work decently well. I would use a PSU without a semi-passive functionality in this case to make sure there is a minimum of airflow over the components at all times.