Hacker News Reader

Comment by rubyn00bie | Hacker News Reader

Anyone know why they chose a consumer grade CPU on this? I’m a little surprised to see a 9950X as the top option. There’s not enough PCIe lanes available to run everything without bifurcation. I imagine the GPUs probably aren’t too bothered generally… but the NVMe drives are likely to slow down as a result.

A Threadripper ain’t cheap, but if you’re spending $45k on a workstation it seems like a weird place to skimp. Not to mention you’d then have the option of shoveling a few more 6000 pros in it when you want to run something larger (assuming your home/office electrical box can support it).

View on HN

The GPUs might care quite a bit about bifurcation. The RTX Pro 6000s can communicate directly between themselves over PCIe 5.0 16x and saturate the bus doing so. This is used when doing tensor parallel LLM execution for the All-Reduce steps.

Someone can work around this by including a PCIe 5.0 switch like the Broadcom PEX89048. That switch can be used to, for instance, have the two GPUs talk to each other at full PCIe 5.0 16x speeds, while talking to the motherboard at say PCIe 4.0 16x, or even 8x. As an end user, cards using that switch seem to be an AliExpress only item, but I assume an OEM like System76 could get their hands on it to place directly on the motherboard. I imagine the price of adding that to a motherboard could be less than the price of switching to a Threadripper or Xeon 600 platform.

However, I can't find any evidence that System76 has added a switch, and in fact they refer to x8/x8 multi-GPU support, making me think they didn't add a switch. To my mind, this isn't a very satisfactory setup.

You need far more absurdly expensive RAM (RDIMM/ECC?) for a threadripper. Like 4x more expensive.

Aye but at $45k you’re so deep already is that really worth the savings? It’s so much easier to manage a single system, and the performance will be in absolute terms better.

Truly, I get your point, but $45k is obscene for a workstation (because of the RAM shortage). I can’t fathom it being a reasonable decision[1] unless you’re able to churn an immense profit from it. And… if you can, it’s an expense that saves time, energy, and effort. If it is only profitable when $8k in price difference makes it viable, is that really worth the effort? An $8k increase making a difference, when you’re wholly dependent on the frontier (or near frontier) lab not releasing a model that makes your work(station) irrelevant— seems reckless. Couple that with the doubling of DeepSeek’s parameters for their flash model… and well the math just don’t math for my naive brain.

[1] I’m absolutely incapable of spending that much on a workstation so my opinions may be irrelevant… but I cannot understand the “stepping over quarters to save a penny” mentality[2].

[2] I could be missing the forest for the trees. As a result, I’d love to know how I am being shortsighted. I just can’t fathom a situation where an $8k surcharge in system RAM doesn’t make sense. It’s not about system RAM, it’s about GPU RAM, margins, and useful lifetime of the system.

This is a link to their configurable workstation on consumer boards. They offer TR or Xeon based boards too; it's just a different link/SKU: https://system76.com/desktops/thelio-major

So they offer both options.

> An $8k increase making a difference, when you’re wholly dependent on the frontier (or near frontier) lab not releasing a model that makes your work(station) irrelevant

Hmm, why? I don't understand why better models being available remotely would change the usefulness of what you already have working locally? If it works for you, it works, regardless of what the frontier labs have, and if it doesn't, it doesn't, again regardless.

Reply on news.ycombinator.com