-
Save 15% on ALL SFF Network merch, until Dec 31st! Use code SFF2024 at checkout. Click here!
S4MAX: Brickless S4M w/ 3090 FE and R9 5950x - 800W, 5l, water cooled
- Thread starter petricor
- Start date
Thank you for informing me, this was actually really helpful! I thought metal cooling was like water cooling but on a budget for air coling!
May I ask what the thermals are? I am planning to do the same build but with a custom-built case.
I know this is out of no where, but is it possible for you to make me a tp345 for the 804p, for 3 fans
I have finally upgraded the name of the thread to "3090" - after re-gaining my confidence that this can actually work, which got shaken a little in the past week.
I had a mild heart attack after getting repeat black out/ reboot cycles as soon as I'd do anything beyond just showing the desktop with the 3090 plugged in to the system- and for I while I was concerned I had my math for the PSU wrong, as typically this indicates that the GPU doesn't get enough power...
As I still haven't seen anything packing more power into something that fits the S4M than the Supermicro 804p, this would have been a hard stop for this project. Eventually I got things to run stable with the GPU at an 80% power limit which brings its TDP down from 350W (or 347, to be precise) to the 280W I had running successfully with my 2080ti - but that can't be the solution - and 800w single rail power should indeed be able to cope with what I want to throw at it.
So, next hypothesis: The wiring has too much resistance, and there are a lot of sources on the web explaining how to NOT wire a 3090 to a single power feed and just double up to two PCI connectors at the GPU end, which is what I did for my 2080ti and have recycled here. Most sources claim that is to use two independent power rails at the PSU which makes sense for an ATX PSU, but in my case that should not make a difference as having a single 800w 12V rail - unless there is simply not enough cross section to get the power through.
I had dimensioned my wiring as a single pair of AWG 14 as the bottle neck, which in theory is rated for 80A - that's 960W at 12V so this can't be it, really.
The 3.5mm bullet connectors, however, are much closer to their limits - rated for 40A, they max out at 480W.
Whilst this is all within spec, of course, temperature and resistance goes up with load, and driving something close to capacity for a long period is never a good idea.
Looking at the bullet connectors of my original wiring confirms this - these used to be golden, but now look like they have spent some time in an oven, and that certainly does not contribute to conductivity, and of course they age mechanically, contributing to what may be a resistance problem.
For a test of my hypothesis I solder a new set of wires together, using twice the cross section for the most part bringing down resistance (that applies regardless of rating), and having a set of brand new bullet connectors at the end, for the moment trying to avoid soldering on additional connectors to the PSU before I know that this is actually the problem.
And voila - things run stable at 100% power limit!
As a general precaution, and in preparation for the next challenge in the form of cooling, I have read a bit into undervolting (OptimumTech has great guides on both the 5950x and 3080/3090). With my current settings - 15 (strangely unit-less) "counts" down in Precision Boost Overdrive (that's anything between -36 and -60 mV) for the R5950x, and 862mV @ 1866 MHz for the GPU, I beat stock performance for both (north of 20,000 GPU score in TimeSpy), whilst saving 49W TDP for the GPU. I cannot quantify the power savings on the CPU, but even disregarding that, I am now within 14(!)W of my 2080TI/ 3950x setup which I have successfully cooled with my current radiator configuration.
The fan upgrade to a Noctua NH-A14 Industrial should be able to deal with the Delta - that's the plan, at least!
There is one new item on my shopping list for this build though as a result of this detour: A second set of bullet connectors for the PSU-GPU link.
Whilst things now work, the bullet connectors run too close to maximum capacity for comfort, and taking temperature readings whilst running benchmarks confirms:
83 Degrees at the connector! No wonder the last set started looking a bit sad after a while...
And that whilst the PSU is not crossing 40 degrees - so the connectors indeed seem to be the bottle neck in power delivery. Clearly, there is some more soldering ahead... and hopefully some custom parts in the post, soon, to tackle the GPU mod!
I had a mild heart attack after getting repeat black out/ reboot cycles as soon as I'd do anything beyond just showing the desktop with the 3090 plugged in to the system- and for I while I was concerned I had my math for the PSU wrong, as typically this indicates that the GPU doesn't get enough power...
As I still haven't seen anything packing more power into something that fits the S4M than the Supermicro 804p, this would have been a hard stop for this project. Eventually I got things to run stable with the GPU at an 80% power limit which brings its TDP down from 350W (or 347, to be precise) to the 280W I had running successfully with my 2080ti - but that can't be the solution - and 800w single rail power should indeed be able to cope with what I want to throw at it.
So, next hypothesis: The wiring has too much resistance, and there are a lot of sources on the web explaining how to NOT wire a 3090 to a single power feed and just double up to two PCI connectors at the GPU end, which is what I did for my 2080ti and have recycled here. Most sources claim that is to use two independent power rails at the PSU which makes sense for an ATX PSU, but in my case that should not make a difference as having a single 800w 12V rail - unless there is simply not enough cross section to get the power through.
I had dimensioned my wiring as a single pair of AWG 14 as the bottle neck, which in theory is rated for 80A - that's 960W at 12V so this can't be it, really.
The 3.5mm bullet connectors, however, are much closer to their limits - rated for 40A, they max out at 480W.
Whilst this is all within spec, of course, temperature and resistance goes up with load, and driving something close to capacity for a long period is never a good idea.
Looking at the bullet connectors of my original wiring confirms this - these used to be golden, but now look like they have spent some time in an oven, and that certainly does not contribute to conductivity, and of course they age mechanically, contributing to what may be a resistance problem.
For a test of my hypothesis I solder a new set of wires together, using twice the cross section for the most part bringing down resistance (that applies regardless of rating), and having a set of brand new bullet connectors at the end, for the moment trying to avoid soldering on additional connectors to the PSU before I know that this is actually the problem.
And voila - things run stable at 100% power limit!
As a general precaution, and in preparation for the next challenge in the form of cooling, I have read a bit into undervolting (OptimumTech has great guides on both the 5950x and 3080/3090). With my current settings - 15 (strangely unit-less) "counts" down in Precision Boost Overdrive (that's anything between -36 and -60 mV) for the R5950x, and 862mV @ 1866 MHz for the GPU, I beat stock performance for both (north of 20,000 GPU score in TimeSpy), whilst saving 49W TDP for the GPU. I cannot quantify the power savings on the CPU, but even disregarding that, I am now within 14(!)W of my 2080TI/ 3950x setup which I have successfully cooled with my current radiator configuration.
The fan upgrade to a Noctua NH-A14 Industrial should be able to deal with the Delta - that's the plan, at least!
There is one new item on my shopping list for this build though as a result of this detour: A second set of bullet connectors for the PSU-GPU link.
Whilst things now work, the bullet connectors run too close to maximum capacity for comfort, and taking temperature readings whilst running benchmarks confirms:
83 Degrees at the connector! No wonder the last set started looking a bit sad after a while...
And that whilst the PSU is not crossing 40 degrees - so the connectors indeed seem to be the bottle neck in power delivery. Clearly, there is some more soldering ahead... and hopefully some custom parts in the post, soon, to tackle the GPU mod!
Last edited:
Yeah those bullet connectors are usually a bit overrated, they are mainly for RC which rarely sees continuous load.
Yep- will have to build just that! Still trying to find a bunch of cheap ones that I can rip apart for practise
Failing that: Soldering directly to the GPU... that would be next-level excitement that I'd prefer to avoid - but then: Whatever it takes!
Oof, I hope it doesn’t come to that. Here’s a guide Josh put together for ultra low profile cables:Yep- will have to build just that! Still trying to find a bunch of cheap ones that I can rip apart for practise
Failing that: Soldering directly to the GPU... that would be next-level excitement that I'd prefer to avoid - but then: Whatever it takes!
Low profile cables
Wow, I'm so glad I went with a total of 4 bullet connectors for the GPU (2 per lead) on my build!
Oh wow - that's a good one, didn't have that method on the radar: May save my 3090 from getting burned!
This is the way.Wow, I'm so glad I went with a total of 4 bullet connectors for the GPU (2 per lead) on my build!
For reference, could you point me to a product link for those bullet connectors? I can't seem to find connectors like that at Mouser, though I'm likely just terrible at searching. They do look rather handy, even if I've now learned not to run a high powered GPU through just two
That's the ones I have used - not available anymore but there should be plenty to that spec on amazon/ebay; these here look pretty much identical!For reference, could you point me to a product link for those bullet connectors? I can't seem to find connectors like that at Mouser, though I'm likely just terrible at searching. They do look rather handy, even if I've now learned not to run a high powered GPU through just two
Try hobbykingFor reference, could you point me to a product link for those bullet connectors? I can't seem to find connectors like that at Mouser, though I'm likely just terrible at searching. They do look rather handy, even if I've now learned not to run a high powered GPU through just two
Similar threads
