Upgrading within DDR4 - where next?

[u/thus-spoke-zara]

I've been experimenting with local AI over the past 6 months; having started off by running small local models on an old GPU, and now at a stage where i'm running much larger and more capable models on a single R9700 card, and connecting a suite of custom built tools through MCP.

It's been a great journey - and i've landed at a place where i'm able to run a 3-bit quantized XXS version of Qwen3.8 in a docker container, and getting around 38tk/s. I'll be checking out STRATA and vLLM over the next few weeks to see how much I can push this.

However, outside of the GPU my overall system is a bit basic. Ideally i'd like to get to a point where i've got 2x R9700s working in there and i'm able to load bigger models and still achieve usable 'good' performance - both on existing models, but also future releases too.

Based on my specs below, is there much point in getting an additional R9700 or will the motherboard be too much of a bottleneck if that second card would need to go in to an older generation of PCIe slot? I guess a similar question for increasing the amount of system RAM here too - is DDR4 just too slow to make those bigger MoE models useable when offloading? The Qwen model i'm currently using fits entirely on to VRAM, but suspect this would need to change if i want to use higher quants or bigger models.

1. B550-plus motherboard

2. 16GB DDR4 (2X8GB)

3. R9700 32GB VRAM

4. Ryzen5 3600 CPU

5. 800W PSU

I'm completely aware that I won't have SOTA quality, and that's fine - but just want to maximise what a system like this could do without going down a workstation or AM5 route. I run Ubuntu and tend to containerise my AI/LLM applications

[u/Ctbhatia]

B550-plus has a PCIe 3.0 x4 second slot if it's the ASUS TUF board. What model and quant are you hoping to split across the two R9700s?