Mac Studio M3 Ultra 256 GB vs Mac Studio M3 Ultra 512 GB
M3 Ultra 256 GB has 256 GB memory, 819 GB/s bandwidth, 270 W nominal power; M3 Ultra 512 GB has 512 GB memory, 819 GB/s bandwidth, 280 W nominal power. Compare model compatibility, like-for-like tokens/sec and ownership cost below.
Verdict
- throughputAcross 4 like-for-like model configurations, decode throughput is within 10% — close enough that the difference is smaller than the uncertainty in the underlying evidence.
- capacityBoth machines run all 8 compared models in their best practical configurations. Compare their quantizations and evidence labels before treating any throughput difference as a hardware result.
- costAt 8 hours a day, the Mac Studio M3 Ultra 256 GB has approximately 31% lower total monthly cost ($60 against $87), for a C corporation in United States (federal).
- evidenceAll 4 like-for-like throughput rows are estimates. Treat the ranking as indicative and the margins as uncertain.
- recommendationThroughput is close enough to be a wash, so this comes down to cost and capacity: the Mac Studio M3 Ultra 256 GB is cheaper to own, and capacity differences above decide which models you can run at all.
Every statement above is generated from the calculations on this page by fixed rules — no prose is written for individual comparisons. If the numbers change, the verdict changes with them.
Hardware
| Mac Studio M3 Ultra 256 GB | Mac Studio M3 Ultra 512 GB | |
|---|---|---|
| Purchase price estimate | $5,674 * | $8,287 * |
| Memory | 256 GB | 512 GB |
| Memory bandwidth | 819 GB/s | 819 GB/s |
| Usable bandwidth indicator | 580 GB/s (71%) | 580 GB/s (71%) |
| Nominal power | 270 W | 280 W |
| Measured load power | 195 W | 205 W |
| Idle power | 12 W | 13 W |
| Architecture | unified memory | unified memory |
Like-for-like performance4 comparable models
GLM-5.3 FlashTernary Bonsai 2 27BDeepSeek-V4.1 FlashMiMo-V2.5 310B-A15BMiMo-V2.6 Flash 309B-A15BDeepSeek-V4 FlashHunyuan Hy3DeepSeek Coder V2 236B-A21B
| Model | Mac Studio M3 Ultra 256 GB | Mac Studio M3 Ultra 512 GB | Winner |
|---|---|---|---|
| GLM-5.3 Flash 321.323B (18B active) | ~35.4–51 t/s Q4_K_M | ~35.4–51 t/s Q4_K_M | Tie (0%) estimated · estimator_v1 · 8K context |
| Ternary Bonsai 2 27B 27.36B | — no matched configuration | — no matched configuration | Not comparable |
| DeepSeek-V4.1 Flash 763.205B (16B active) | — no matched configuration | — no matched configuration | Not comparable |
| MiMo-V2.5 310B-A15B 310.775B (15B active) | ~42.2–60.7 t/s Q4_K_M | ~42.2–60.7 t/s Q4_K_M | Tie (0%) estimated · estimator_v1 · 8K context |
| MiMo-V2.6 Flash 309B-A15B 309B (15B active) | — no matched configuration | — no matched configuration | Not comparable |
| DeepSeek-V4 Flash 304.18B (13B active) | ~48.3–69.5 t/s Q4_K_M | ~48.3–69.5 t/s Q4_K_M | Tie (0%) estimated · estimator_v1 · 8K context |
| Hunyuan Hy3 298.786B (21B active) | ~30.6–44 t/s Q4_K_M | ~30.6–44 t/s Q4_K_M | Tie (0%) estimated · estimator_v1 · 8K context |
| DeepSeek Coder V2 236B-A21B 235.741B (21B active) | — no matched configuration | — no matched configuration | Not comparable |
Hardware deltas are calculated only when quantization, runtime, exact context, execution/decode mode and relevant inference settings match. Measured and estimated results are never compared to each other. A difference under 10% is reported as a tie.
Best practical configuration
| Model | Mac Studio M3 Ultra 256 GB | Mac Studio M3 Ultra 512 GB | Practical result |
|---|---|---|---|
| GLM-5.3 Flash | ~35.4–51 t/s Q4_K_M · estimated | ~20.6–29.7 t/s Q8_0 · estimated | Both fit; configurations may differ |
| Ternary Bonsai 2 27B | — PTQ1_0 · estimated | — PTQ1_0 · estimated | Both fit; configurations may differ |
| DeepSeek-V4.1 Flash | — DS4 V4.1 Q2 (SSD) · estimated | — DS4 V4.1 Q2 (SSD) · estimated | Both fit; configurations may differ |
| MiMo-V2.5 310B-A15B | ~42.2–60.7 t/s Q4_K_M · estimated | ~24.6–35.4 t/s Q8_0 · estimated | Both fit; configurations may differ |
| MiMo-V2.6 Flash 309B-A15B | — Q4_K_M · estimated | — Q8_0 · estimated | Both fit; configurations may differ |
| DeepSeek-V4 Flash | ~51.8–74.5 t/s MLX 4-bit · estimated | ~28.3–40.7 t/s Q8_0 · estimated | Both fit; configurations may differ |
| Hunyuan Hy3 | ~32.9–47.3 t/s MLX 4-bit · estimated | ~17.7–25.5 t/s Q8_0 · estimated | Both fit; configurations may differ |
| DeepSeek Coder V2 236B-A21B | — Q5_K_M · estimated | — Q8_0 · estimated | Both fit; configurations may differ |
This is a deployment comparison: each machine uses its own recommended configuration. Different quantizations can change speed and quality, so these figures are not raw hardware benchmarks.
Economics — United States (federal), C corporation, 8h/day
| Mac Studio M3 Ultra 256 GB | Mac Studio M3 Ultra 512 GB | |
|---|---|---|
| Purchase price estimate | $5,674 | $8,287 |
| Reclaimable VAT | $0 | $0 |
| Net cash at purchase | $5,674 | $8,287 |
| Monthly depreciation | $66.20 | $96.68 |
| Monthly electricity | $1.20 (9 kWh) | $1.27 (9 kWh) |
| Tax programme | §179 100.0% | §179 100.0% |
| Tax-programme benefit | $1,192 | $1,740 |
| Monthly economic cost | $59.58 | $86.63 |
| Total over 5 years | $3,575 | $5,198 |
Purchase prices are localized inputs in USD: tax/VAT excluded for Mac Studio M3 Ultra 256 GB and tax/VAT excluded for Mac Studio M3 Ultra 512 GB. Net cash and monthly economic cost then apply the selected United States (federal) / C corporation tax treatment. Tax assumptions last verified 2026-09-07. Federal planning estimate only, not tax advice. State and local income tax, sales/use tax and incentives are excluded. It assumes 100% business use, a Section 179 election, enough business income to use it, and that the full annual limit remains available.