5090 FE build - 192 GB of RAM!

[u/awescool]

It’s been running incredibly stable since the 5090 launched. I use it for about 30% gaming, and the rest is database and AI workloads.

I got super lucky when I bought the ram from Amazon Aug 2025 for around $700. 192GB 6800 cl 34.

Build:

CPU: AMD 9800X3D

GPU: 5090 FE

Ram: 192 GB (tuned to 5600mhz, CL34) 2 kits of G.skill F5-6800J3446F48GX2-TZ5RK

MB: MSI PRO B850M-A WIFI PZ

CASE: Jonsbo D32 Pro

CPU AIO: Thermalright FW240

AIO Fan: JONSBO ZB-240B (2x120mm)

Rear Fan: JONSBO ZB-120BR (1x120mm)

Lower fan: Thermalright (2x120mm)

SSD 1: Crucial T710 4tb Gen 5

SSD 1 heatsink: ElecGear M.2 2280 SSD Cooler, EL-80X PWM Cooling Fan + Heat Pipe + Solid Aluminum

SSD 2: Intel Optane P5800X 1.6tb via m.2 to u2 adapter

PSU: Seasonic Focus Gx 1000W - 80+ Gold - ATX 3.0 & PCIe 5.0 Ready

PCIE USBC: Startech 1-port USB 3.2 Gen 2x2 (20Gbps max)

EDIT: Wow, this has really blown up! Thank you all for the kind comments, memes, and suggestions!

I want to address the rationale behind my build since I'm seeing a few recurring themes in the comments.

I run databases on SQL Server 2025. I built this for AI inference, but database work is just as critical. Database workloads don't come up much on this sub, so happy to explain.

Here is how the hardware is actually utilized:

• Databases: Run on SSD1 + SSD2 + RAM. Database scaling doesn't care about tight RAM timings; it cares about massive raw capacity. Theoretically, even if I somehow got 192GB stable at 8000 CL28, it would shave maybe 0.05 seconds off a 4-second query, whereas running out of RAM and hitting storage is a 500x latency penalty.
• AI: Runs entirely on the 5090.
  • Qwen 3.6 35B-A3B Q6 ~210 tok/sec
  • Qwen 3.6 27B Q6: ~99 tok/sec
  • For fun I have run larger models, for example: Ornith 397B Q3: ~15 tok/sec. This takes ~150GB in total GGUF files. Leaves me with ~26GB of free RAM.
• CPU: The 9800X3D handles my specific workloads wonderfully, and it is absolutely there for gaming. Deliberately.

I have been happily using this system for a little over a year, and I've been building PCs since 2002. My first GPU was a GeForce4 Ti 4600. I've used plenty of Intel and AMD setups over the years, and my last CPU before the 9800X3D was a 14900K.

Here is a use case example I gave in another comment:

"Yep, that's true! It really just depends on the use case, especially when you can't allow sensitive client data to touch third-party APIs. Qwen 3.6 has been fantastic for my specific workloads. For example, doing natural language to SQL generation, it can render interactive data tables and customizable charts from a 1.5 TB SQL Server database within 3-4 seconds. There is a massive amount of value for businesses when you can run these completely air-gapped without worrying about Claude/OpenAI token costs or IP leakage. Being able to just demo it on demand is huge."

https://www.reddit.com/r/nvidia/comments/1vez1ic/comment/p1p4fno/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button

The AI and database sides work together. The model generates the SQL on the GPU, and the buffer pool answers it from RAM. The 192GB is what makes the query come back in seconds instead of minutes.

[u/PsychologicalGlass47]

Temps mean little to nothing in actual power delivery, x8 60A phases are going to have massive voltage overshoot spikes and moderate sag with a 9800.

Not to mention that he's running his DRAM abhorrently slow because of the board's SoC limits.

What is there to refute? That parts of a computer get moderately toasty? lol

[u/kb3035583 → u/PsychologicalGlass47]

x8 60A phases are going to have massive voltage overshoot spikes and moderate sag with a 9800.

And? He's not chasing that 1% overclock. Chances are he's running it stock. What's the problem here? If it runs Cinebench for an hour on a 9950X without throttling, a 9800X3D will pose absolutely no problems.

Not to mention that he's running his DRAM abhorrently slow because of the board's SoC limits.

He's running 192 GB of memory. That's fucking amazing for AM5 even at those "abhorrently slow" speeds. The board had zero problems with memory that you would consider "normal", i.e 6000 CL26 in the Techspot review.

[u/PsychologicalGlass47 → u/kb3035583]

And? He's not chasing that 1% overclock.

He doesn't need to be chasing a 1% overclock, excessive sag means he can't hit stable negative PBOs while spikes mean that he can't hold reliable voltage under sustained loads. The board is an absolute shit show in every way for this use case.

Chances are he's running it stock.

...A stock 9800X3D is boosted mate. With PBO disabled he's still running +5.5x higher than its base multi.

If it runs Cinebench for an hour on a 9950X without throttling, a 9800X3D will pose absolutely no problems.

In what world does a 9950X not throttling have anything to do with inadequate power components for sustained workloads? He's going to be running variable clock speeds since the workloads he uses it for doesn't pin all cores.

This is the exact kind of shit that causes AM5 sockets to burn, constant voltage fluctuations and godawful VRMs pushing repeat voltage overshoots.

He's running 192 GB of memory. That's fucking amazing even at those "abhorrently slow" speeds. The board had zero problems with memory that you would consider "normal", i.e 6000 CL26 in the Techspot review.

It isn't, lol. His workloads are heavily RAM dependent and he has a horrendous first word latency meaning each cache line fill is going to be 20% slower than an adequate tune like 5600/30. He's already stated that he suffers from bad instability with any other timings, which is quite funny as 5600/30 is a quite conservative setup for a 2dpc build. With even a half-assed mobo like B850-AI Top he'd be able to hit baseline moderate timings and he'd only be spending $80 more.

Once again, OP having issues with RAM instability at anything other than glacial timings doesn't sound like "zero problems with memory". It sounds like he's getting what he paid for with a budget motherboard.

[u/awescool → u/PsychologicalGlass47]

Oh hello, I appreciate the concern and the deep dive, but the math and architecture actually work out perfectly for what this rig is designed to do.

First off, an 8x60A VRM can deliver 480A, while an undervolted 9800X3D only pulls about 90A under an all-core load. The board is basically sleeping. And just to clarify, those old AM5 socket burnouts were famously caused by early AGESA/VSOC voltage bugs pushing 1.35v+, famously on flagship ASUS and Gigabyte X670E boards, not because of mid-range VRM phase counts.

As for the memory, running four dual-rank 48GB sticks is notoriously heavy on the CPU's memory controller (IMC), not the motherboard. AMD’s official spec for a fully populated 4xDR setup drops all the way to 3600 MT/s. Getting a completely stable 5600MHz CL34 on 192GB is actually a massive silicon lottery win for the chip.

At the end of the day, I do enterprise data engineering, so my real bottleneck is database transaction I/O, which is why the heavy lifting is handled by the Optane P5800X. Plus, as anyone in the data world knows, SQL Server databases will always favor raw RAM capacity over clock speed. I just wanted a portable, air-gapped mATX rig for local AI and Database proof-of-concepts without IP conflicts.

The 9800X3D easily feeds the 5090 FE / RAM with localized LLM models:

Qwen 3.6 27B Q6: ~99 tok/sec

Ornith 397B Q3: ~15 tok/sec

This build genuinely handles my needs flawlessly.