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AI Engineering
Models Under the Hood

Running models on your own machine

A laptop can run a capable small model. It is the fastest way to learn what models need and to keep data private.

Chapter 16: Models Under the HoodLesson 6 of 6Level: CoreAbout 12 min
Words on this page (8)
parameter
: One learned number inside a model. Modern models have billions of them. Training adjusts them.
GPU
: Graphics processing unit. A chip with thousands of cores, ideal for the matrix math in AI.
prompt
: The input text you give a model, including instructions, examples and data.
tool use
: The model asks your program to run a function and reads the result.
tool
: A function the model can ask your program to run, described by a name, description and argument schema.
API
: Application programming interface: a way for one program to call another, usually over HTTP.
context window
: The maximum number of tokens a model can look at in one call: your prompt, the conversation, tool results and the answer together.
token
: A piece of text the model reads and writes, usually a word or part of a word. About 4 characters of English on average.

Getting started

Install Ollama or LM Studio, then pull a model with one command. Choose a size your memory can hold. As a rule, a 4-bit model needs about half a gigabyte per billion plus some overhead. So 8 GB of memory fits roughly a 7 to 8 billion parameter model. Unified memory on Apple Silicon lets the use system memory, which is why laptops handle larger models than a typical PC graphics card.

What to use them for

Classification, extraction, summaries and drafting where the data should not leave your machine. Local models are also a cheap test bed for and . Expect weaker results than the frontier on hard reasoning and coding. Most local runners expose an compatible with the common cloud APIs, so your code can switch with a changed URL.

A worked example: what fits

A 7 to 8 billion parameter model at 4-bit is about 4.5 GB, comfortable on a laptop with 16 GB of memory. A 14B model is about 8 GB, tighter. A 70B model at 4-bit is about 40 GB, needing a workstation. Start with the small one and see if it is good enough for your task.

A memory budget in practice

The rule of half a gigabyte per billion parameters ignores everything else on the machine. On a 16 GB laptop, the system and open apps may take 4 to 5 GB (invented, check your own). That leaves about 11 GB. A 14B model at 4-bit needs about 7 GB, and the context cache adds one or two more, so it fits. A 32B model needs 32 × 0.5 = 16 GB and does not.

What goes wrong: it slows to a crawl

If the model plus its cache is larger than free memory, the system pushes part of it to disk. The symptom is words arriving every few seconds and a laptop that gets hot and stuck. To confirm, open the memory monitor while it generates and look for heavy swap use or memory pressure in the red. Choose a smaller model or a more compressed version. Another symptom is a model that ignores the start of a long document. Many runners start with a short by default, so early text is silently dropped. Paste a document with a fact in the first line, ask about it, and raise the context setting if the answer misses.

Try it yourself: is it good enough

Write 20 real prompts from your task and run them on the local model and a cloud model. Mark each answer acceptable or not. If the local model passes 18 of 20 and the cloud one 19, the local model is good enough. Also note speed. Around 5 to 8 a second is close to reading speed, so slower than that feels sluggish.

When the cloud wins

One laptop serves one request at a time well. If a hundred people need answers together, or the task needs hard multi-step reasoning, a hosted model fits better.

Common mistake

Expecting a laptop model to match the largest cloud models.

Check yourself

Roughly how much memory does a 4-bit 8B model need?

Why switch to a local model for some work?

Your laptop has 8 GB of memory. Which model size is realistic at 4-bit?

Go deeper

  • Repo
    OllamaRepo★ 184k

    Ollama · The simplest way to run models locally.

  • Tool

    LM Studio · A desktop app for downloading and chatting with local models.

  • Repo
    llama.cppRepo★ 132k

    ggml · The engine behind many local tools.

  • Tool

    Community · The main community for local model news and tips.

Spotted a mistake or something unclear? Report it on GitHub.

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