A good preview admits what it predicts
Llmspeed lets a reader choose hardware, a model, and a quantization. It then simulates the wait before the first token and streams sample text at the predicted decode rate. The site labels each result as measured, derived, or projected. It also states that drivers, engine versions, flash attention, power limits, and thermals can move real results by 10 to 30 percent.
The public repository makes the mechanism inspectable. At revision 671c918, the calculator reads package size, estimated key-value cache, usable memory, backend coefficients, context depth, and active weight bytes. It uses separate paths for exact catalog combinations, formula-based projections, and partial offload. Those constants explain the preview. They do not turn the preview into a measurement on your machine.
Prediction quality is one question. Workload fit is another.
Measured still needs a test shape
Llmspeed asks benchmark contributors to run llama-bench -m your-model.gguf -p 512 -n 128. A submission records the hardware, model, quantization, backend, engine version, generation rate, prompt-processing rate, prompt size, source URL, and unusual settings.
The llama.cpp documentation keeps prompt processing and text generation separate. It repeats each test, reports an average and standard deviation, and can place the test at a chosen context depth. It also says the timer excludes tokenization and sampling. A measured decode rate can be valid while omitting startup, first response, tool calls, file reads, and retries.
A new model card does not fill the hardware row
DeepSeek published DeepSeek-V4.1-Flash-1017 today. Its model card lists 763 billion parameters, a one-million-token context window, and twelve linked quantizations. It reports publisher benchmark gains across coding and agent tasks. The card does not provide a consumer-machine throughput result for your chosen quantization and engine.
The release is a useful example because three questions arrive together. Can a package fit? Can the runtime serve it at an acceptable rate? Does it finish your coding work with fewer wrong turns? A model benchmark answers the third question only inside its named harness. A speed preview addresses parts of the first two. Neither replaces a matched local run.
Time the job, not only the decoder
Record cold load, first response, prompt processing, text generation, and total task time. Keep the prompt and generated token counts beside those clocks. Then replay a small coding workload with the same tools, repository, context policy, and stop rules you plan to use.
If the model spills weights into system memory, record that route. If a runtime update changes the result, record both revisions. If the fast setup needs another attempt after a bad edit, keep the retry in the task clock. Tokens per second describe one moving part.
Use the preview as a filter
- Choose two or three setups that appear to fit the model and budget.
- Pin one model artifact, quantization, and engine revision.
- Run prompt-processing and generation tests at a realistic context depth.
- Replay the same held-out coding tasks on every setup.
- Compare total task time, memory pressure, wrong actions, and recovery.