RX 7900 XT 20GBBudget pick
20 GB VRAM (+4)800 GB/s (+288)
A
Raises estimated decode speed by about 49%.98 tok/s decode
Raises estimated decode speed by about 49%.
Adds memory headroom for longer context windows and future model growth.
~$899 MSRP
Can MPT-7B-Instruct run on RX 6800 16GB?
YES — Tight Fit
B69Good
○Estimated from fit model
MPT-7B-Instruct needs ~14.6 GB VRAM. RX 6800 16GB has 16.0 GB. With Q4_K_M quantization, expect ~66 tok/s.
Runtime: llama.cppCapacity: TightBandwidth: MediumStack: StandardBottleneck: Balanced
Share:
Operating mode
Choose the run profile you care about
Interactive favors responsiveness, while light API and scale-out lean harder on serving readiness. The fit stays the same, but the recommendation lens changes.
Current mode
Balanced
Balanced for general local use. Keeps the ranking neutral across personal and serving workflows.
Select quantization to explore
Q4_K_M (Medium quality) — 14.6 GB, 65.9 tok/s, Tight fit
14.6 GB required16.0 GB available
91% VRAM used
Fit status
Tight fit
Decode
65.9 tok/s
TTFT
2936 ms
Safe context
8K
Memory
14.6 GB / 16.0 GB
Memory breakdown
Weights4.3 GB
KV Cache7.8 GB
Runtime0.9 GB
Headroom1.6 GB
See how fast it feels
See how fast it feelsMPT-7B-Instruct on RX 6800 16GB
1st promptCold start — includes initialization
>Solve: If a train travels at 60 mph for 2.5 hours, how far does it go?
Let me work through this step by step.
Given information:
- Speed = 60 mph (miles per hour)
- Time = 2.5 hours
Formula: Distance = Speed x Time
Calculation:
Distance = 60 mph x 2.5 h
= 150 miles
The train travels 150 miles.
Double-check: at 60 mph the train covers 60 miles each hour. In half an hour it covers 30 miles. So in 2.5 hours: 60 + 60 + 30 = 150 miles. Confirmed.
2nd promptWarm — model ready, no init overhead
>What if the train stops for 20 minutes halfway?
The stop doesn't change the total distance covered while moving, but it affects total trip time.
Breakdown:
- First half: 1.25 hours at 60 mph = 75 miles
- Stop: 20 minutes (no distance)
- Second half: 1.25 hours at 60 mph = 75 miles
Total distance: 150 miles (same)
Total time: 2.5 h + 0.33 h = 2.83 hours
Average speed: 150 / 2.83 = 53 mph
The distance stays the same but average speed drops to 53 mph because of the stop.
Estimated: 65.9 tok/s decode · 2.9s TTFT (warm) · 165 tok/s prefill
What limits this setup
This setup is broadly balanced for this model.
No major red flags
This recommendation has enough memory headroom and acceptable estimated speed for the selected workload.
Best improvement path
Performance by workload
| Workload | Grade | Fit | Decode | TTFT | Context |
|---|---|---|---|---|---|
| Chat | A | Runs well | 65.9 tok/s | 1601 ms | 8K |
| Coding | B | Tight fit | 65.9 tok/s | 2936 ms | 8K |
| Agentic Coding | F | Too heavy | 24.4 tok/s | 11555 ms | 8K |
| Reasoning | B | Tight fit | 65.9 tok/s | 3469 ms | 8K |
| RAG | F | Too heavy | 24.4 tok/s | 14443 ms | 8K |
Quantization options
How MPT-7B-Instruct (7B params) fits at each quantization level on RX 6800 16GB (16.0 GB usable).
| Quant | Bits | VRAM | Quality | Fit |
|---|---|---|---|---|
Q2_K | 2 | 2.7 GB | Low | B63 |
Q3_K_S | 3 | 3.4 GB | Low | B63 |
NVFP4 | 4 | 3.9 GB | Medium | B64 |
Q4_K_M | 4 | 4.3 GB | Medium | B64 |
Q5_K_M | 5 | 5.0 GB | High | B65 |
Q6_K | 6 | 5.7 GB | High | B66 |
Q8_0Best for your GPU | 8 | 7.5 GB | Very High | B67 |
F16 | 16 | 14.3 GB | Maximum | F0 |
Get started
Copy-paste commands to run MPT-7B-Instruct on your machine.
Run
lms load mpt-7b-instruct && lms server startUpgrade options