Log *complete* S4MAX'23 / World's smallest 4090 build: Brickless 5l S4Mini, 4090FE, 7950X3D, 800W, water cooled

petricor

Airflow Optimizer
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May 12, 2018
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It looks like this is happening - and about 5 minutes on Google tell me that no one crammed a 4090 into a 5l case as of yet so until someone proves me wrong I'll go with this rather bold headline!

After quite some pondering over the basics and some preliminary testing, I'm reasonably confident that this can work - with the usual 3 challenges in mind:
Power, heat, space - this one will be fun!


Preliminary list of ingredients:
• Case: Skyreach 4 Mini, as usual (yes I will be cannibalizing my last build here)
• Front Bezel: My custom S4 Mini Heat Sink Bezel, machined from Aluminum, anodized black
• Board: Asus Rog Strix B650E-I (more on why that's not a ROG Strix X670E-I later)
• RAM: 2x16 GB G.SKILL Flare X.5 DDR-5 6000 CL32-38-38-96
• GPU: NVidia RTX 4090 FE
• SSD: Samsung 980 Pro 1TB (Gen5 is - at present - a space issue... may evolve!)
• Radiator: AlphaCool Nexxxos 140.v2
• Pump: AlphaCool DC-LT 2600 with Alphacool Eisstation 40-DC reservoir and a 6/8mm soft tubing circuit
• CPU Water Block: the unobtainable original EK Annihilator
• GPU Water Block: Modded Corsair HydroX 4090 FE with custom Plexi top
• Fan: Noctua A14 industrialPPC-3000 with Aquacomputer Quadro for controls
• PSU: Modded SuperMicro PWS804-r, 800w/12V single rail
• Fittings: Predominantly Festo G1/8, with a couple of Koolance NZL ultra-low profile G1/4 elbows between radiator and pump
• Riser: custom-made LinkUp PCIe4 cable
...so no too drastic departure from my last build - cooling, power, and case remain in place, everything transporting electrons at high frequencies is new, and the cooling will need to learn a few new tricks.


And here's the plan:

From the outside, it looks identical to the previous version (it's the same case and bezel after all)...



...and the basic layout is pretty similar to what I came up with for my 3090 & 5950X build:



And as you may see, my intention here is to not start meddling with too many different parts but to keep the motherboard's I/O shield and cooling assembly intact bar for some decorative plastic (my previous builds required quite a lot of modifications to fit the GPU and block - and I had some interference issues resulting from removing parts of the I/O shield) and even leave the board's active VRM cooler in place. Also, I want to use the original ram heatsinks as DDR 6000 without cooling would appear a bit overly ambitious.



To make this work without cutting into motherboard parts or other components, my 4090 / water block combo will have to become smaller and thinner than the 3090 solution I came up with - and I intend to do this by building the world's smallest water block for a 4090. Well - at least smaller than this one, and if @optimumtech did their research well, which I assume, I conclude that I beat Alphacool as what I am currently designing is smaller in every dimension - that's, of course, presuming it works!
As in my previous builds, it will sit on top of the CPU with the first-gen EK Annihilator - out of production since 2016 but still, the smallest AM5-capable block that I am aware of.


So much for the general ambition - let's start by looking at the basics for heat and power:

There is a lot of talk about 1000w being the minimum for a 4090 and top-end CPU - doing the math using the nominal TDP figures, I get to 450W (4090) + 120W (R9 7950X3D) + 65W (rest of the system, on a bad day) - totaling to 635W... so that should be a reasonably comfortable fit with my 800W PSU. Well, it better be, as to date this is still the most compact PSU mod I am aware of, and still, the apparent maximum I can cram into an S4Mini. Conveniently, I have a year-long track record of running a 3090+5950X with this PSU, so rather than starting my calculations from scratch, I can work with the deltas:
The CPU should be not too much of a concern. Even though the IRL power consumption of a 7950x3d with sustained all-core load is a staggering 150W, it's only marginally more than the 136W peak of my current 5950X (which I heavily overvolt for stability reasons - so it's probably quite a bit more) - and, luckily, much less than the 240W loaded power draw of the 7950x.
The 4090, however, comes with more of an uplift compared to its predecessor: IRL, benchmark tests suggest that the 4090 pulls around 420W at 98% utilization - that's giving me some more headroom compared to TDP, on the other hand though, it's considerably more than the 366W IRL sustained load power draw of the 3090FE I currently use on my PSU.


So, altogether still within the theoretical margins or the PSU, but 70W (or around 15%) more than my current build, having an impact on both heat and power.

Regarding heat, I'll be pretty much stuck with my current layout as there is no way to cram more than my current 140mm rad into this build: But with CPU temps in the low 70s and water in the mid-50s under load, I believe it is possible as I have two variables to play with: Currently, the air intake to the radiator is through the case's ventilation slots with about 35% opening ratio. Cutting out the fan projection from the bottom of the case and inserting a thin mesh instead should significantly improve airflow should I run into trouble, and that without tampering with anything visible. And as a second option, lowering the GPUs power limit would suggest being a very effective measure (https://www.hardwaretimes.com/nvidi...performance-at-4k-with-a-power-limit-of-300w/) - this should shave off in excess of 100W of peak load, bringing the thermal load below my 3090/5950X system whilst hardly sacrificing any performance.


But that's the theory -and as usual, there is only one way to find out:





Enter my new 4090FE! I guess I am committed now...
(and a few unboxing shots - looks like they have excess engineering capacity at NVidia directed at inventing rather impressive cardboard mechanics...)

Whilst they are quite a common sight by now, they are incredibly hard to come by in Europe (well, I'm in the UK but that's the same for this purpose): NVidia sold probably 3 to each major retailer and then made them disappear after the first batch - with only 3rd party or reference designs being available. Normally that's not an issue, but if you're in for SFF, you will eventually realize that, like with the 3090s, the FEs have by far the most compact PCB footprint - and that's a decisive enabler for this build.


But we're not there yet:


Here it is in all its voluminous glory next to my 3090 build - beautifully engineered, only a tad too large for what I have in mind for it!

First goalpost is getting it running on my current setup and stressing it to see whether the power setup works (well it better does - no plan B here!) - so I need to build an adapter for my single-rail 12V PSU turning two bullet connectors into 16 pins for a GPU. After triple checking pin-outs (don't want to fry that thing before it fired up once...)


...I get to this beauty...


...which plugs into 3 of 4 8-pins of Nvidias monstrous 12VHPWR (the name is as clumsy as the actual thing) adapter.
Should do the trick.

Frankensteining this together, I should now have a setup that is a pretty good representation of my planned power layout, ready to fire up...



...and: It's alive!

Admittedly, that's low-hanging fruit - the real test is what happens when I stress the system.
Running various stress tests and a few rounds of Port Royal, I get no stability issues whatsoever, and a score of >25,000 indicating that the GPU is happy with the power it can draw:


Also, PSU temps remain very reasonable - so that's the first box "Power" ticked!

Well... apart from that funny smell of heated electronics.
Looking at all temperature sensors I cannot fathom the issue - everything is well within margins, but something is definitely off.
Not intending to burn or electrocute myself, I scan the setup with my temperature gun - and well...


...it looks like my 18AWG wiring between PSU and GPU is not quite happy with the power draw of the 4090 ;)
This will definitely need an upgrade - and possibly also new/ different bullet connectors. Technically they are within specs for the wattage I pull, that said, I believe the surface coating on them is cheap and suffered when soldering them on - it looks like the hotspot is near or at the connectors.


Happy I found that out on an open bench - that could have been a flamboyant feature!

Up next: Space and layout considerations - and the water block design (just sent out to manufacturers for quotes...)
 
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princess_daphie

Cable-Tie Ninja
Jan 26, 2019
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Impressive challenge!!!

I only had one thought. If you're going so far as to mod this thing and cram so much in a tight space, you should straight up make a custom 12 pin connector to go directly from the 4090 to your PSU, using the proper gauge etc.
 

petricor

Airflow Optimizer
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May 12, 2018
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Impressive challenge!!!

I only had one thought. If you're going so far as to mod this thing and cram so much in a tight space, you should straight up make a custom 12 pin connector to go directly from the 4090 to your PSU, using the proper gauge etc.
Yeah that's definitely the plan - what I show here was a quick fix to test the PSU... that NVidia adapter alone wouldn't fit anywhere in the case.
 

mikejmcfarlane

Average Stuffer
Apr 19, 2022
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This is such an impressive challenge, can't wait for the next installment.

The CPU should be not too much of a concern. Even though the IRL power consumption of a 7950x3d with sustained all-core load is a staggering 150W, it's only marginally more than the 136W peak of my current 5950X (which I heavily overvolt for stability reasons - so it's probably quite a bit more) - and, luckily, much less than the 240W loaded power draw of the 7950x.

Sorry if a dumb Q. Why are you overvolting for stability? Are you also overclocking that 5950X?
 

petricor

Airflow Optimizer
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May 12, 2018
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This is such an impressive challenge, can't wait for the next installment.



Sorry if a dumb Q. Why are you overvolting for stability? Are you also overclocking that 5950X?
The first batches had issues and technically I got a broken CPU - it didn't even make it past the boot screen on stock settings ... and as I did not want to go through a lengthy RMA process I instead resorted to this post here based on Buildzoid's ZEN 3 BIOS review - essentially overvolting the SOC to improve memory stability, whilst using and undervolting curve by @optimumtech as in here in parallel to drive up core boost frequencies - did the trick and runs rock stable
 
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petricor

Airflow Optimizer
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So, space and layout - I'll explain the plan bottom-up starting with the m-ITX board - enter the next box!


Within, the Asus Rog Strix B650E-I - coming out on top of my features-for-volume tradeoffs:


My initial preference has been the Rog Strix X670E-I as being the only X670 m-ITX I'm aware of - and with it the only 40GBit USB4/TB4 m-itx option.
This feature set comes with a pretty hefty volume price tag though: The board needs two daughterboards to cram all of this into an m-itx form factor and still needs to resort to an external DAC module for audio processing.


Photo: Asus

Whilst the SATA daughter board (1) is optional (that said, it also contains the jumper to set the PCIe x16 slot to gen 3 which isn't something you'd necessarily want to lose looking at the limited choice of compact risers, and the limited utility of Gen4 for present gen GPUs), the second daughter board (2) contains the second Promontory21 chip forming a rather prominent tower - and both would collide with my GPU and the x16 riser cable connecting it.
Whilst theoretically, the board should work without the second chip, I'd effectively downgrade it to a B650 (an X670 is a B650 with a second Promontory21 chip) and forego the option of a Gen5 M.2 slot (3), plus losing a bunch of PCIe lanes that will cut off some devices - and, unfortunately, there is no clear documentation as to which ones may be affected.

So, ultimately, a stripped-down version of the X670 would give me less functionality than a B650 - for significantly more money, plus, depending on which Promontory21 connects to the TB chip, potentially not even giving me the benefit of the standout feature - the 40GBit TB4 connection.

And that's where the B650 comes in:



It comes with a whole bunch of accessories - SATA cables, zip ties, wifi antenna, and replacement thermal pads for M.2 drives (nice touch)- but, notably, no external DAC, and most importantly:


No SATA daughter board, and a much lower "tower" - and above it is where my GPU will need to live for my layout to work.

The only feature I'd love to have and miss here is the 40GB USB4/TB4 spec on the USB port as it would give me a more or less reliable way to drive an Apple Studio Display - the B650 gives me a 20GBPS DP over USB3.2 that exceeds the TB3 spec and may potentially deliver the signal required - whether that ultimately works remains to be tested.

As mentioned in my previous post, I'll try to modify fewer parts compared to my previous builds by redesigning the GPU block (more on that later), and in the case of the board, I'll resort to only getting rid of decorative elements.



The ROG STRIX B650E-I comes across refreshingly lean, and the rather comfortable keep-out zones around the CPU should leave me enough space to route the cooling loop around it.


Ridding it of some decorative elements reveals the key potential for this build - the optionality of the M.2 tower. Unlike the X670, the tower does not contain any parts of the chipset, but merely the DAC and a Gen5 M.2 slot...

... and removing it leaves me with a fully functional board with a chipset heat sink not exceeding the height of the PCIe slot, and on top of that even an optical SPDIF audio port directly on the board allowing me to connect it to a DAC of my choosing if required...


...and in all likelihood, I'll not connect any audio device directly to the box so the audio processor is an element I'm happy to sacrifice anyway.

Another important feature that sets it apart from the X670 is a Gen4 M.2 slot on the bottom side of the board:

This allows it to drive a Samsung 980 pro in the absence of the "tower" on the top side - the X670 has both M.2 slots on the top side, so even removing the daughter board with half of the chipset would leave me with an M.2 drive plus heat sink projecting into the build volume.
With all that said, using the considerably lower "tower" on the B650 and potentially a Gen5 M.2 is not entirely off the table yet - I currently look into loop layouts that may allow me to keep it in place.


Next is memory: With the AM5 platform comes a requirement for DDR5 Memory of the EXPO variety - and comparing models available with the ambition to keep the heat sinks intact, G.Skill FlareX5 sticks come with the lowest profile I could find on the market - the 6000MHz CL32 kit should be at the performance sweet spot for the 7950x3D...


...and, most importantly, it is only...

...projecting 33mm above the board, giving me about 15mm of clear space between RAM top edge and case which should be enough to fit my redesigned GPU block.

Installed, it gets me to a reasonably compact package for the board and memory with comfortable clearances around it...


...which gets me to the CPU Block as the next key element of the build:


As mentioned in my last post, I have chosen to resort to the original EK Annihilator I use in my current R9 5950X build implying that I need to cannibalise it- and I won't rip it apart before some of my custom parts have arrived as unfortunately it's out of production since 2016 and virtually unobtainable. Getting hold of the one I currently use was pretty adventurous and involved getting a reseller list from EK and checking inventories, finding what appeared to be the last one on a shelf anywhere on the planet - and buying it from a store in New Zealand with the help of @confusis.

To my great surprise, no one managed to build anything nearly as compact since - I had hopes for EKs new EK-Pro as suggested by @NinoPecorino to be a fit, also to make this build reproducible - but unfortunately its much more voluminous and would make my loop layout impossible:


Visualising it on the B650 board...


...shows you how much more space it takes...



...in comparison to the original EK Annihilator...


...and interestingly, the smaller EK Annihilator has a larger contact plate than the more voluminous EK-Pro - the performance should be well-comparable.
Note to my future self: Design a compact CPU block...

So, with the block in place, the board-memory-cpu assembly it intended to fit into the S4 Mini as intended by @Josh | NFC - with 6mm clearance between the board and case bottom. In my previous build, I had to lower the board by 3mm into the case to increase the clearance for the Corsair GPU block to fit over the CPU - this led to a bit of a squeeze at the rear I/O panel.


With my own slimmer GPU block redesign (more detail to follow), I should be looking at a stack that fits with default board clearances.

In front of the board goes my Supermicro PWS-804r PSU mod...


...and next to it is an AlphaCool Nexxxos 140.v2 radiator.


This gets connected to a AlphaCool DC-LT 2600 with Alphacool Eisstation 40-DC reservoir using two Koolance NZL ultra-low profile G1/4 rotary elbow adapters...


...and topped off with a Noctua A14 industrialPPC-3000.


Next comes the 8mm OD loop - and here I'll develop two options in parallel, allowing me to potentially enable a top-mounted Gen5 M.2 drive:


Loop A is the safe option assuming the absence of a top-mounted DAC/M.2 tower:

This leaves clearance for both water out- and return tubes to run to the rear of the PCIe slot - the connections (1) and (2) are for water in/out to the GPU block, respectively.


I have a custom LinkUp Gen4 riser in the making - the cables will be a bit thicker compared to the Gen3 riser I use at present - and depending on how it fits, I may even be able to use Loop B below:


The red block is the DAC/Gen5 M.2 assembly modelled to the top surface of a standard M.2 drive - what's missing is a heat sink; the one coming with the B650E-I would not fit, but I'm fairly confident that I'll find a low profile aftermarket part that fits the bill; I may even connect it to the GPU block above it.

Loop B will require routing the water return tube to the front side of the PCIe slot resulting in a significantly longer loop and less space for the riser cable - may or may not pan out but definitely worth a try! I will not order a gen5 drive before that is confirmed to work though...

You can see how both loops use the pocket next to the wifi module to tuck in a connection to the GPU - this is the decisive layout enabler allowing me to fit a 4090 on top of this stack - more on that later.

The last key component is my custom GPU/Block assembly - 19mm thick on average and 23mm at the highest point.

Whilst the 4090 PCB layout makes this assembly slightly bigger in footprint compared to my 3090FE with a custom port module (I have been able to mod a smaller 3080 block to fit the 3090- not an option here), the reduction in height I achieved through redesigning the plexi top of the block should allow me to fit it precisely between PSU and board heart sink - and the 4090s horizontal power connector certainly helps here as not projecting vertically into the build as with the 3090 - modding OTS L-Adapters such as these should do the trick for a straight forward power connection (2x12AWG) and routing it along the cases outer top edge.


So much for the layout-
up next: Designing the world's most compact 4090 Water Block!
 
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petricor

Airflow Optimizer
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None of the pictures in your current post are visible, seem to have broken links. Website issue ?
yeah just saw that - no clue what's going on as they show when drafting and they disappear when saving... using same hoster (imgur) as usual...
 
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petricor

Airflow Optimizer
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hmmm... no luck with images... the bbcode is correct...
 
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