I’m looking to build a new PC(which I’ve never done, other than upgrade my current one) for running and fine tuning 7b models. I know I’ll be getting dual 3090 or 4090 GPU, but I’m not sure which CPU would be best for this.
I’m wanting to take advantage of the bundle deals at my local micro center and down to these two options:
- AMD Ryzen 9 7900x 4.5ghz 12 core, Asus B650E-F motherboard and 65GB DDR5 for $600
- Intel i9 14900k 3.2ghz 24 core, MSI Z790 MAG Tomahawk motherboard and 65gb DDR5 for $800
Anyone know which would be best for my use case? I don’t mind spending the extra $200, I only want the best option of the two
Thanks in advance
Hmm. Im not a fan of the 7900x. It has two CCUs like the 7950x, but only 6 cores per. It ends up being pretty awkward in practice on my 7950x3d. I’d recommend going all in on a 7950x, or do a 7800x3d. Im not educated on if the extra cache benefits LLM, but it’s a fantastic value for the money.
The lopsided CCUs in X3D parts are not the same as the ones on 7900X/7950X. The cache ensures that you need a scheduler that can put loads that need it on the cache-enabled portion and that’s asking a lot from a scheduler. The AMD parts without extra cache don’t suffer from this issue… it’s why I got a 7950X, but the 7900X is also fine and all three of these CPUs will be entirely limited by memory bandwidth if used for CPU inference.
Information moving between CCU’s is troublesome with certain workloads. I’m not referring to the lopsided cache, but rather the limitations of what is basically two CPUs merged together and the complications that adds to their shared I/O.
I don’t recommend the 7900x because it is a failed 7950x. I recommend the 7800x3D and the 7950X as long as the prices are within stretching for. The 7950x3D fits a very niche role as well.
Go with Intel.
I’ve got a 7950x with a B650E MB and have had nothing but problems
What kind of problems have you ran into?
I would say research the CPU/MOBO combo, not just the CPU. In addition: make sure you buy RAM which is on the Mobo manufacturer’s supported list. I have a Ryzen 7 5800 and an MSI MAG B550 TOMAHAWK motherboard. Not gonna lie, I always consider AMD a risk due to chipset related quirks I have experienced with previous builds, but it has been fine so far.
If you’re planning on running the models entirely on the GPUs, your choice of CPU won’t really affect the speeds you are getting. I’d go with the Intel since this is your first PC build, I built a 7950X rig a couple months ago. I didn’t have problems getting it to boot, but it absolutely had a fit over running 4 sticks of DDR5-6000 at their rated speed. The rated speed is really only valid for 2 sticks.
I’m in the same boat trying to build a 2x3090 PC. I’m thinking of going Intel because of the stability. The other issue is finding the right motherboard to support both the physical size of the GPUs and the PCIe 4.0 lanes (both size and if the mobo will fully utilize it) and not to mention the thermals and case/fans considerations.
Let me know your specs and what you end up going with as I’m figuring this all out as I go.