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Choosing a CPU

I’m looking to build a new rig for machine learning and software development.

I’ve kind of settled on getting an Nvidia A6000 as my GPU, starting with just one for now, but possibly getting more in the future if needed – realistically I can see myself adding one more, but having the ability to upgrade my system up to 4 A6000s like this build does look very appealing.

I was originally considering the Threadripper 3960x (or if I feel like spending a bit more a 3970x), which seemed like the best fit for a build like this. The problem is that I feel like an idiot buying a Zen 2 chip that was released in 2019 in 2021. There are some rumors of new chips coming out in November, does it make sense to wait until then? But then who knows if they are really going to be released and available then.

One alternative I’m looking at would be a Ryzen 9 5950X, which is only around half of what the TR costs giving me nice savings. I would probably get better single-threaded performance (which may be nice for some use cases), and having 16 cores still isn’t bad, but it does seem that I would have to limit the future upgradability of my build to two GPUs only due to the number of PCI lanes available. Anything else to keep in mind when choosing between a TR and Ryzen 9?

The other option would be a Milan EPYC chip (something like a 7443P?) but it makes me a bit worried about potential compatibility issues I may face using a server board. On the other hand, I would get practically unlimited upgradability in terms of adding more GPUs and anything else I might need. Is there anyone with experience using an EPYC as a desktop/workstation CPU? I’ll be using Linux so I don’t care about Windows drivers.

One last consideration for me is that I want to install a Gigabyte Titan Ridge 2.0 which should be able to take in two DisplayPort connections from my GPU and merge them into a single Thunderbolt cable, which is needed for my LG Ultrafine 5k monitor. There seems to be one Designare MB for TR CPUs which even comes with the card, but I’m wondering if I can get it working on other motherboards too. I’ve read people just short some pins on the cable that’s supposed to go into the motherboard so it may not matter very much which MB I choose.

Ryzen platform doesn’t offer enough PCIe lanes to meet your demands. Unless you want to stick with a single A6000 and buy a new system once you get additional GPUs.

Threadripper with 4x A6000? Sorry to say, but you’ll get close to PCIe lanes maximum and most TRX40 boards don’t even have 4x PCIe x16 slots. And we haven’t put any Nvme or Thunderbolt addin cards yet. 4x GPU+Thunderbolt+NIC and/or nvme? No way you can run this on a TRX40.

But there is Threadripper Pro, which is what you are looking for. Plenty of Lanes, plenty of slots, plenty of features for professionals. And you can get the cheapskate 3955wx with 16 Cores, which isn’t available for normal Threadripper.

Thunderbolt support isn’t exclusive to the Gigabyte boards with addon cards. Can’t remember if the Asus Sage for TR Pro has it, but we got people here in the forums with that board.

Although new Threadrippers seem to be on the horizon, I doubt that we see new Threadripper Pro CPUs soon. The OEMs certainly want their headstart again. I’m waiting for Threadripper 5000 series, but I’d buy now and not wait for new Pro CPUs.

Thanks, Exard3k. So it seems like if I don’t want to sacrifice upgradability I want either a TR Pro (a new version of which won’t be coming out soon anyway) or I need to look into using the EPYC in a workstation.

Regarding Thunderbolt the point seems to be the ability to take two DP connections and send them over a single Thunderbolt cable for my monitor. This guy got it working. You have to physically plug in two cables from your GPU into the extension board from the outside (it’s a bit ugly but it works). I believe the monitor behaves as two 4K monitors which are then tiled to produce a 5K image. It’s meant to be used with Apple laptops and Apple being Apple has their own way of doing things, although to theirs and LG’s defense the monitor did come out before DP 1.4 was widely available and the 5K resolution doesn’t work over a single DP 1.2 lane. There’s a refreshed version that may not require all this but I have the original one.

As far as I have seen, there is no Thunderbolt support on EPYC boards. But please double check as I’m not an expert on EPYC boards, but they are generally geared towards server use,

Threadripper Pro is meant to be the Server platform for workstations while still retaining server-grade features like IPMI and full 128 lanes and 8-channel memory. Wendell called it a “Sworkstation” once, a very fitting name. Because I wouldn’t call 7x PCIe x 16 slots a desktop board by any means.

Be sure to check Thunderbolt compatibility with your board and OS. Thunderbolt may be a standard, but implementation varies greatly and can result in all kinds of troubles depending on your use case.

You’re right, the Threadripper Pro motherboards look exactly like what I’m looking for whereas the server boards for Epyc will bring considerably more trouble. On the other hand, the 3rd gen Epyc is a new chip released early this year and my understanding is that the TR Pro and Epyc are very similar in many ways, but with the Epyc I’m getting newer technology (Zen 3). I’ll be reading through this thread to learn a bit more.