Janky Intel Mainboard mod to enable iGPU on a board without iGPU power rail

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I’ve posted this before at the eevblog forum, however I didn’t get any response even though it got a good amount of views

So I hope to get some feedback

So the goal is to supply vccgt on a mainboard that doesn’t have a vccgt rail.

Board: Fujitsu D3373-A11

Why: I want to use software features that rely on the iGPU, and for that the iGPU needs voltage - Intel spec is 1.05V

Why not use another board?:
I’m in Germany and idle power is of crucial importance and fujitsu boards are very efficient due to good bios support for c-states and 12v only PSU.
Check out this idle power ranking from hardwarelux:

Also the board is very cheap and the bios can be modded to support up to Intel core 9th Gen.

Anyway the board does not have an iGPU rail but its got everything else I want…

The Plan:

This is the pinout for socket

The grey lower left is vccgt, which is the iGPU rail

The main issue is that there is only one place I can connect to, to supply the voltage and that are vias on the backside of the socket

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So as you can see the vccgt vias are surrounded by vcore infill.

Issue 1:
So the plan would be to xacto knife cut the vcore infill surrounding the vias of from the vcore power plane. Scrape of the solder mask and use the cut off vcore infill (now it would be not connected to anything) and use it as vccGT powerplane.

Issue 2:
Now I’d have a exposed vccgt plane to solder to, but there is still no vccgt rail… So the plan is to use Vmem from the ddr4 vrm 1.2v its closest to the 1.05v Intel spec and powerful enough

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So I’d double or triple the filtering cap on the memory vrm and connect a wire to the ‘new vccgt plane’

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Also I’d preferably drop the voltage 100mv, I thought maybe a schottky diode but I like some advice. Max amperage should be 20A. typical 1A - 10A

Issue 3:
I’d like filtering mlc’s at the new vccgt plane but the only ground anyware close is at the through hole caps from the vcore vrm. So I’d run a copper foil from the ground pin at the vcore caps to right beside the new vccgt plane and than add same mlc’s across.

Issues 4:
Power sequencing - I don’t really have an answer to this issue I can’t find a Intel skylake power sequence diagram. Maybe someone knows something about it…

So if you people can advice me if the plan is sound or if I missed something.

Thanks for helping !

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This sounds like a very bad idea and you are risking frying your CPU and MB here.

A few things regarding the mod:

  • Even if you supply the iGPU power rails, there is no guarantee that the iGPU will actually work, as it might require other things that may not be present on your board (both in hardware and in firmware).
  • Supplying a 1.05v rail with something that’s not 1.05v is generally not a good idea if you don’t know what you are doing. If you really wanted to I’d recommend getting an external power regulator

Real solution in my opinion:
Get a 12th/13th gen Atom platform or something similar that is intended for low power applications.

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I get what you are saying its a 25$ c236 board with the pcie layout I need and I how what I’m doing also I’d test the board with some shitty celeron g3900. So the risk is slim

So if you can name a board with a x8x8x4x4pcie layout, 6 sata, ecc support, similar ilde power and 6-8core, remote management, dual gigabit intel lan and intel igpu for less than 100$ I’m all ear’s

Also just because I want low ilde power doesnt mean I dont want perfomance, something in the range 6-8core coffelake

On the hardware side the igpu just needs vccGT and software I got covered

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So you’d use something like this

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Those things don’t really exist in modern platforms for that cheap

You clearly didn’t read reviews of 12th and 13th gen Atom (including N series Pentium and Core i3). Those things use the E-cores from higher end CPUs instead of the same old Atom cores. They can be had in up to 8 core configurations.

Probably not that beefy but yes something like this

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I’d say you’d struggle get that for 500$ on 12/13 gen

I did read them, and thats why I concluded that this is the only board that fits my needs

  • Alder Lake-N is to my understanding just e-cores and they are about as fast as skylake and kaby lake

  • No ECC

  • 16gb max, i forgot to mention i need at least 64gb better 96gb/128gb

  • single channel

  • Pretty much no pcie lanes

regarding i3 i got an i3 12100 on asus h610 mini itx and msi b660-m and idle power is considerably worse

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The one platform you might score something is Zen2 / Zen3 APUs (4000 and 5000 G series CPUs)

Coffee Lake is basically just Kaby Lake so there’s not much of a difference

By this point I think you’re asking something that almost doesn’t exist.

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zen has just terrible ilde power consumption, embedded Epyc maybe - but I really dont want soldered cpus.

There are just a few ryzen in this list also ryzen 4/5xxxg would need to be pro for ecc

Your right, coffee lake is very close to kabylake, it just clocks better and has more cache and compared to alderlake n it got hyperthreading.

Exactly as I said:

I know there is nothing quit like it thats why i made this plan

I even brought a supermirco x11sca-f and idle power also poor 36watts same c state: c7 with a g5400 dual core

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The ones with integrated GPUs and the ones without are completely different things. The ones with integrated GPUs are monolithic and don’t have the power consumption problems of the Chiplet ones.

It’s more likely that few people tested those configs.

If you are willing to go as far as physically mess around with CPU power rails I don’t think needing Pro series CPUs is going to be much of an issue

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Completly different is a little rich, its the same architecture, yes the G no-multichips are more power efficent, but its the same issue in red mainbaord with remote managment and igpu

https://www.asrockrack.com/general/productdetail.asp?Model=X470D4U#Manual

Besides not having the x8x8x4x4 pcie layout I cant be sure it actually runs the igpu

I’m willing to go to those length if the price is right - I wouldnt do it on a 400$ Mainboard.

This is a 25$ mainboard with xeon its less than 100$ total, it got everything I want, it just needs vccGT

nothing else even come close to the features I want, power efficiency and cost

a ryzen pro ist easily over 100$, am4 server mainboard 200$+ atleast.

I’m cheap, if I wasnt I’d just run one of the many servers I’ve around and just pay for the 100+ watt idle power

11

I love projects like this. That’s a lot of amperage for a reasonably sized diode to eat and not detonate.

If I was going to try this I’d explore a few options,:

  1. you could use a step down converter off of the power supply, maybe between the 5v and 3.3v rail so you’re only going from 1.7v down to whatever you need. This would be my rock and stick solution.

  2. what is vcore on this board? Maybe you can pull directly from that

  3. maybe there are unpopulated component pads for the igpu power rail?

This is a situation where a good variable output power supply would come in handy, test the theory in the simplest way possible first.

Also, people over and under volt hardware all the time. There is probably some amount of deviation from spec where it would still function.

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  1. [quote=“wizarddata, post:11, topic:202537”]
    you could use a step down converter off of the power supply, maybe between the 5v and 3.3v rail so you’re only going from 1.7v down to whatever you need. This would be my rock and stick solution.
    [/quote]

I’d rather not do it like this. I’d like to have no external circuts

  1. [quote=“wizarddata, post:11, topic:202537”]
    what is vcore on this board? Maybe you can pull directly from that
    [/quote]
    It would run Intel 8/9th gen, so 0.7v-1,2v svid controlled and thats the main issue c-states and 0,7V for a 1.05vccGT is certainly not enough and I want the great energy efficency that fujitsu board provide and I dont want to raise the Vcore while idle.

  2. [quote=“wizarddata, post:11, topic:202537”]
    maybe there are unpopulated component pads for the igpu power rail?
    [/quote]

Sadly no there is just nothing. The only trace of vccGT are the vias on the back.

IMG_20231020_113441826~6
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White: Ground, Yellow:VccGT, Purple: Vias to drill out

In the next couple of days I’ll do a test with my proof of concept board I’ll just use a pentium g4400 and grab the 1.2V vccMem. Also there is the BIOS issue, it turned out to be more involved than I though but its should be fine. And maybe the iGPU get’s picked up by windows/linux

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How sure are you that the memory power rail can supply the necessary current? It’ll be interesting to find out.

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The memory vrm uses a 0902nsi low side fet from Infineon

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and since the buck converter drops 12 to 1.2 the low side does most of the work anyway I feel pretty good about the current handling even with the igpu

Intel specs the igpu in absolut maximum current at 45A depending on model.

My xeon is 45Watt Tdp so i’d say its a fair guess that it wouldnt pull 45A rather maybe 25A at worst and ddr4 with 4 dimms will not exceed 15A - so I add a headsink to the high and low side fet’s to be on the safe side.

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SUCCESS:
IGPU online:

igpu_test_ubuntu
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Windows:

IMG_20231026_205619732
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IMG_20231026_205917687
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VccMem is quite high with 1.225v and one 18awg wire is probebly not enough but igpu online :blush:

6 Likes
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Yes! That’s awesome.

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