Speed vs Quality: Comparing LFM2, Qwen3, and DeepSeek-R1 on a Local APU
The Question
In a previous post I found that qwen3:30b-a3b runs at 12 TPS on my AMD APU (Ryzen 5800U, 64GB DDR4), beating every other model on the system by exploiting Mixture-of-Experts to keep active parameters low. Then lfm2:24b-a2b arrived and hit 17.8 TPS — 47% faster — using a hybrid SSM+MoE architecture.
But tokens per second is only half the story. A model that answers faster but worse is not a better model. This post compares three architecturally distinct models on the same hardware across reasoning, synthesis, and analytical tasks.
The Contenders
| Model | Architecture | TPS (Matt-Mini) | What makes it distinctive |
|---|---|---|---|
lfm2:24b-a2b |
Hybrid SSM+MoE | 17.8 | No KV cache (SSM), ~2B active params |
qwen3:30b-a3b |
MoE Transformer | 12.0 | 3B active params, built-in thinking mode |
deepseek-r1:14b |
Dense Transformer | 3.1 | Reinforcement-learning trained reasoner |
All running on Matt-Mini: AMD Ryzen 5800U, 64GB DDR4 (~50 GB/s bandwidth), AMD Vega 8 iGPU via Ollama's Vulkan backend.
Test 1: Formal Logic (Einstein's Puzzle)
The classic five-houses logic puzzle — 15 clues, five attributes per house, one correct solution. This tests structured multi-step deduction: can the model hold state, backtrack when it hits a contradiction, and reach a definite answer?
LFM2:24b-a2b — 17.8 TPS
LFM2 engaged immediately with a clear systematic approach, correctly anchoring on the fixed clues (Norwegian in house 1, house 3 drinks milk, house 2 is blue), then working through colour placement. Crucially, when it hit a contradiction — incorrectly placing green at house 3 which conflicted with the coffee/milk clue — it identified the error and self-corrected:
"Wait — green house is house 3, drinks milk — but clue 5 says green house drinks coffee. Contradiction! So our earlier assumption must be wrong. Let's recheck green/white placement."
It then correctly revised to green=4, white=5, and continued building the solution. At 2000 tokens it was still mid-deduction (the puzzle typically requires 2500–3500 tokens to complete), but the reasoning quality was coherent throughout with no hallucinated leaps. The self-correction under contradiction is the key capability here — many smaller models simply assert a wrong answer.
Qwen3:30b-a3b — 12.0 TPS
Qwen3's thinking mode is enabled by default. Given a 2000-token budget, the model consumed all 2000 tokens in internal reasoning and produced no visible output. This is not a failure of reasoning — it is a consequence of extended chain-of-thought: Qwen3 thinks before it writes, and for a complex puzzle, that thinking budget was exhausted before the answer appeared.
The practical implication: At 12 TPS, giving Qwen3 enough tokens to complete a hard logic problem (say 4000 tokens total — 2000 thinking, 2000 answer) means waiting ~5–6 minutes with nothing visible on screen until the model finishes thinking. For interactive use, this requires either disabling thinking mode (/no_think suffix or think: false in the API) or accepting the latency.
DeepSeek-R1:14b — 3.1 TPS
Same issue, worse TPS. At 3.1 TPS, 4000 tokens takes 21 minutes. DeepSeek-R1 is a dedicated reasoning model — the chain-of-thought is the point — but on bandwidth-constrained hardware the combination of dense architecture (no MoE savings), slow TPS, and long thinking chains makes it painful for interactive reasoning tasks. It is the right tool for problems where correctness matters more than speed and you are willing to wait.
The Thinking-Model Problem on Slow Hardware
This test uncovered a fundamental tension that does not appear in benchmark numbers:
Thinking models have a token overhead that multiplies with your hardware's latency.
On a GPU running at 50 TPS, Qwen3 spending 1000 tokens on internal reasoning costs 20 seconds. On an APU at 12 TPS, the same thinking costs 83 seconds — and you see nothing during that time. DeepSeek-R1 at 3.1 TPS spending 2000 tokens thinking costs 10.7 minutes of silence.
This creates a counterintuitive outcome: LFM2, which does not use extended chain-of-thought by default, feels smarter in interactive use on slow hardware — not because it reasons better, but because it shows its work in real-time rather than batching it invisibly. The perceived quality advantage is partly architectural and partly latency psychology.
For batch or automated tasks (where you submit a prompt and retrieve the answer later), thinking models regain their advantage. For interactive research assistance where you are iterating on prompts, fast transparent reasoning often beats slow invisible reasoning.
Test 2: Research Synthesis
Prompt: Advise on running the best LLM for general-purpose research on an AMD APU (Ryzen 5800U, 64GB DDR4, ~50 GB/s). Compare (a) large MoE with few active params, (b) hybrid SSM+MoE, (c) small dense transformer. Cover speed, quality, context handling, and give a recommendation.
Note: Qwen3 and DeepSeek-R1 were run with thinking disabled (think: false) so their responses are direct rather than chain-of-thought.
LFM2:24b-a2b — 17.8 TPS
LFM2 gave a well-structured response covering all three categories with accurate technical descriptions. On MoE it correctly identified the active-parameter advantage and low-bandwidth benefit. On SSM+MoE it correctly described the KV cache elimination benefit. On dense transformers it correctly explained the bandwidth bottleneck.
One notable weakness: it mentioned "AMD XDNA or ROCm kernels for optimal speed" — technically inaccurate for an Ollama/Vulkan setup. It conflated the architecture's theoretical requirements with platform-specific details it was uncertain about. This is a common failure mode in synthesis tasks: confident-sounding specifics that are slightly wrong.
Qwen3:30b-a3b — 12.0 TPS (thinking disabled)
With thinking disabled, Qwen3 produced a response that read as an externalised internal monologue — thinking-as-prose rather than a structured answer. It walked through the problem step-by-step in first person ("Let me break this down... Wait, the user said..."), ultimately recommending a small dense model like Mistral 7B.
This recommendation is wrong for this specific hardware, and interestingly, Qwen3 is itself running on this hardware. It gave generic advice calibrated to typical CPU inference bottlenecks rather than the actual measured results. It also suggested llama.cpp "15–25 TPS on a 5800U for a 7B Q4_K_M model" — a reasonable estimate for CPU-only inference, but ignoring the iGPU Vulkan backend that gives the measured 12 TPS for a 30B MoE model.
The knowledge cutoff problem: Qwen3 has no training data on LFM2 or the specific benchmark results for this hardware. It gave the best answer it could from general principles, and those principles pointed it toward the wrong conclusion. The model recommended a 7B dense model when the empirical data shows a 24B hybrid SSM+MoE outperforms it by a significant margin on this exact configuration.
DeepSeek-R1:14b — 3.1 TPS (thinking disabled)
DeepSeek-R1's response was clean and well-structured, but contained a clear hallucination: it described SSM as "Switched Sparse Memory" — a fabricated expansion of the acronym. SSM stands for State Space Model, a fundamentally different concept.
Its recommendation — large MoE transformer — was directionally correct, citing that "~50 GB/s is high bandwidth." This is precisely backwards: 50 GB/s is the bottleneck on this hardware, not an advantage. The model interpreted the bandwidth figure in absolute terms rather than relative to the model's memory requirements.
Despite these errors, the structural reasoning was sound: MoE's active-parameter reduction is the right lever to pull on bandwidth-constrained hardware. It got to the right answer via partially wrong reasoning.
Test 3: Critical Analysis
Prompt: Analyse the claim: "Q4 always reduces model quality compared to Q8, so for serious research you should always use Q8." Give a rigorous assessment.
This is a well-defined analytical task with a clear correct answer. All three models had relevant training data. This is where quality differences should be most visible.
LFM2:24b-a2b — 17.8 TPS
LFM2 identified three flaws in the claim:
- Universal claim without qualification — Q4 vs Q8 impact depends on architecture, task, calibration, and hardware. "Always" is unjustified.
- Ignores hardware acceleration — AVX_VNNI provides INT8 dot product acceleration; on AVX_VNNI CPUs, Q8_0 carries no compute overhead, changing the tradeoff entirely.
- Task-specific sensitivity — Coarse reasoning is less sensitive to precision loss than fine-grained factual recall.
The hardware-specific point about AVX_VNNI is precisely the kind of nuance that matters for the actual decision. This was accurate and practically useful.
Qwen3:30b-a3b — 12.0 TPS (thinking disabled)
Qwen3 gave the most thorough response of the three, leading with the logical structure: the word "always" is a universal quantifier that is falsified by a single counterexample. It cited concrete benchmark evidence — Q4 on Llama 3 and Mistral models incurs less than 1% absolute accuracy loss on MMLU vs Q8 — and identified multiple factors the claim ignores: quantisation-aware training, task sensitivity, model architecture, and implicit regularisation effects.
It also identified a counterintuitive scenario: some models fine-tuned with quantisation-aware training show no significant degradation at Q4, or in edge cases slight improvements due to regularisation. This is a more complete analysis than LFM2's.
The response was cut at 1000 tokens mid-sentence, suggesting there was more to come. The quality of what was produced was high.
DeepSeek-R1:14b — 3.1 TPS (thinking disabled)
DeepSeek-R1 produced the most concise response. It correctly identified the binary framing as the flaw (Q4 offers 16 values, Q8 offers 256 — but this alone doesn't determine quality impact), and noted that the practical effect depends on the model and task. The response was shorter and less detailed than the others, but accurate within its scope.
At 3.1 TPS, the time cost of a thorough analysis at DeepSeek-R1's depth is high. For tasks where analysis quality scales with thoroughness, the slow TPS compounds against you.
What the Tests Reveal
On factual accuracy
All three models made errors on the synthesis task — LFM2 got a platform detail wrong, Qwen3 gave the wrong recommendation, DeepSeek-R1 hallucinated an acronym expansion. The analysis task showed higher accuracy across all three, because the claim being analysed is well within their training distribution. Models are more reliable on tasks that resemble their training data. Novel hardware configurations and cutting-edge model architectures fall outside that zone.
On reasoning quality
For the logic puzzle, LFM2's transparent step-by-step reasoning with explicit self-correction was more useful interactively than Qwen3's silent exhausted thinking budget. On the analysis task, Qwen3 produced the most thorough and structured response when thinking was disabled — the base model quality is high when it actually produces output.
On the thinking-mode tradeoff
Thinking mode is a quality multiplier. But on hardware where generation is slow, it is also a latency multiplier — and one that applies silently before you see any output. The practical rule for APU-class hardware:
- Interactive use: Disable thinking (
think: falseor/no_think). You get the answer faster, and for most tasks the quality loss is modest. - Batch / overnight analysis: Enable thinking and set a high token budget. You submit the job, come back later, get a more thorough answer.
LFM2 sidesteps this entirely: its architecture doesn't separate thinking from output, so you see the reasoning in real-time as it generates.
Summary: When to Use Each Model
| Scenario | Best choice | Why |
|---|---|---|
| Interactive research, iterative queries | lfm2:24b-a2b |
Fastest, transparent reasoning, good synthesis |
| Hard reasoning, batch mode | deepseek-r1:14b |
Dedicated reasoner; worth the wait |
| Thorough structured analysis, batch mode | qwen3:30b-a3b (thinking enabled) |
Best analysis quality when given token budget |
| Code generation | qwen3-coder:30b-a3b-q4_K_M |
Specialised fine-tune, 12 TPS |
| Long document analysis | lfm2:24b-a2b |
SSM avoids KV cache growth at long context |
| Uncensored / sensitive research | qwen3.5-abliterated:35b-a3b-q4_K |
No guardrails, 4.65 TPS |
| Quick simple queries | qwen3:8b |
5.3 TPS, low overhead |
The key finding
Speed and quality are not independent on bandwidth-constrained hardware. A model that is four times slower doesn't just cost you time — it changes the nature of the interaction. Thinking modes that are near-free on a GPU become minutes-long commitments on an APU, turning iterative exploration into batch processing. LFM2's hybrid SSM+MoE architecture produces the best combination of speed and quality for interactive use on this hardware, not because it is the most capable model in isolation, but because it delivers its capability at a speed that keeps research workflows fluid.
Appendix: Hardware and Setup
Matt-Mini:
- CPU: AMD Ryzen 7 5800U (Zen 3, no AVX_VNNI)
- iGPU: AMD Radeon Vega 8 (shared DDR4, ~50 GB/s)
- RAM: 64GB DDR4-3200
- Inference: Ollama 0.20.6 + Vulkan backend
API note: Thinking can be disabled per-request via "think": false in the Ollama generate payload, or by appending /no_think to the prompt for Qwen3 models. DeepSeek-R1 respects think: false at the API level.
Tested April 2026.
