This is a build log for workstation-2: a four-GPU rtx6000pro workstation that lives in my office. It’s what workstation-1 wanted to be.

workstation-2 as it runs now — glass off, four cards, the Mellanox card down low

workstation-1 taught me the one thing I needed to start this build: four cards fit in a Dark Base Pro, but four cards don’t cool in a Dark Base Pro. Coolant sat at 45-47°C and the fans had to scream to hold it, which is the exact opposite of livable. So workstation-2 started from a different question — not “how many GPUs can I cram in” but “how much radiator can I fit around four of them.” The answer was a Corsair 9000D, the only case I could find with roughly double the rad area, and pretty much everything else followed from that.

The two constraints didn’t change from the first build: ~1600W out of a normal 120V wall, and a machine I can actually sit next to and take a call.

Power#

Same wall, same ~1600W ceiling (the napkin math is over in workstation-1 if you want it). The thing that gets genuinely tight at four cards is the budget: 4× 300W max-qs is 1,200W before the CPU, RAM, drives, or pump pull a single watt. A Threadripper PRO 9965WX will happily eat 350W if you let it, and 1200 + 350 + platform overhead sails right past 1600.

So I capped the CPU at 4.0 GHz all-core. I don’t need the clocks for inference, I need the watts for GPUs — easy trade. The numbers came out closer than I’d like but they came out: theoretical worst case if everything peaks at once is ~1771W, real flat-out GPU load measures ~1450W, and I ran it pegged at ~1600W for over an hour with no OCP trips. PSU sits around 90% loaded at full tilt, which is thin on purpose.

dry-fitting the loop with the first card in — rads, reservoir, and tubing all coming together

Livability#

I love sitting next to this thing. When I’m chatting with it i can hear the fans slowly ramp (they ramp with coolant temp), never getting too loud but giving you audible and immediate feedback when you are using it. Fun! The loop is 2x480mm rads up front 2x360mm up top, push-pull fans and 3 case fans too (just for funzies). That’s roughly 2.15× what the Dark Base Pro held, against the same heat. The result is a loop thats perfectly cooled. Coolant sits right around 40°C under a hard burn where workstation-1 ran 45-47, and the fans get to loaf because they have surface area to spare. Four cards cooking and it’s still quiet enough to take a call next to. One feature on the case I loved was the top/bottom rad and fan mounting brackets. made it so nice.

The 9000D's radiator bracket swung out — eight fans going onto one rad, outside the case
The back of the tray, where all those fan cables land

The connections themselves are half the fun. The runs from the rads into the manifold I made as hard connections — rigid links instead of floppy tube everywhere — which keeps the routing tight and tidy.

A hard connection tying a radiator into the loop
Another of the rigid links up top

Lessons Learned#

Like the last one this one had its dissapointments/challenges:

  • I bought an Alphacool block, didn’t look closely enough at which Threadripper generation its mounting actually supported (older ones), and even tho I could tell it wasn’t quite right I tried to make it work. So the bill grew by a brand new ASUS Pro WS WRX90E-SAGE SE and the same CPU block as workstation-1.
  • I’d planned a second pump in parallel for redundancy because at initial dry-fit it looked like there was room. As more parts came in there was just no clean place to put it!
  • Sourcing is its own project. I think in addition to amazon i had 4 other major vendors: NewEgg, PerformacePCs, TitanRig and Optimus. Lots of management of deliveries and waiting for blocking parts (those hard lines on the rads were the last thing to come in and held up build for a week).
The face of a man who has just realized his motherboard is dead
Where the screw stripped and snapped off in the board — the moment it all went wrong

What I run on it today#

I just finished it up so right now I’ve got Nex-N2 running tp=4 on it! Loving it so far and can’t wait to run more stuff on it and break it in for its first training run!

First boot — glass on, four cards, the AA debug LED counting up in the corner

BOM#

Specs reflect the machine as built. Where this differs from earlier planning notes, the as-built configuration wins. A good chunk of this — the four Optimus GPU blocks and the 256GB memory kit — came across from workstation-1.

Core platform

Power

Storage

Cooling — radiators & fans

Cooling — water loop

Networking

  • 1× Mellanox ConnectX dual-port 100GbE — to network workstation-1 and workstation-2 together and (eventually) run models across all their GPUs
  • Onboard Intel X710 dual 10GbE — management / LAN