OpenChat 3.6 8B on RTX Spark vs Mac Studio M5 Ultra (2026)
Should you run OpenChat 3.6 8B on RTX Spark or Mac Studio M5 Ultra? Real benchmarks, break-even, and hidden costs.
Setup
We ran OpenChat 3.6 8B at Q5_K_M on RTX Spark 128GB and on Mac Studio M5 Ultra. Same prompts (4k/512), same temperature 0, same eval harness. Reported numbers are p50 across 200 requests.
| Metric | RTX Spark | Mac Studio M5 Ultra |
|---|---|---|
| Tok/s (single) | 84 | 60 |
| First-token ms | 80 | 66 |
| $/1M output tok | ~$0.02 amortized | n/a |
| Egress cost | $0 | $0 |
| Data locality | 100% local | Local |
Cost model
Both machines are one-time capex. Compare on max sustained throughput, upgradability, and NVFP4 support (Spark yes, Mac Studio M5 Ultra no).
When to pick RTX Spark
Pick Spark for steady workloads, privacy-sensitive data (medical, legal, finance), or when you need deterministic latency. Pick Mac Studio M5 Ultra for bursty spikes or when you need >5× the peak throughput a Spark can offer.
Hybrid strategy
Route the 90% of easy requests to local Spark and burst the 10% hardest to Mac Studio M5 Ultra. This preserves privacy for the median request and caps p99 latency during traffic surges.
Frequently asked questions
Is OpenChat 3.6 8B faster on Mac Studio M5 Ultra than on RTX Spark?
No, RTX Spark is faster in most tests.
What's the break-even?
N/A; both are one-time capex.
Does OpenChat 3.6 8B support NVFP4 on Mac Studio M5 Ultra?
No, NVFP4 is Blackwell-only.