computer science

Posted write

Posted write is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Posted write rather than just read about it. In short: A posted write is a computer bus write transaction that does not wait for a write completion response to indicate success or failure of the write transaction. For a posted write, the CPU assumes that the write cycle will complete with zero wait states, and so doesn't wait for the done.

Key takeaways

Posted write belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Posted write to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Posted write from memory before moving on to harder problems.

Reference excerpt

A posted write is a computer bus write transaction that does not wait for a write completion response to indicate success or failure of the write transaction. For a posted write, the CPU assumes that the write cycle will complete with zero wait states, and so doesn't wait for the done. This speeds up writes considerably. For starters, it doesn't have to wait for the done response, but it also allows for better pipelining of the datapath without much performance penalty. A non-posted write requires that a bus transaction responds with a write completion response to indicate success or failure of the transaction, and is naturally much slower than a posted write since it requires a round trip delay similar to read bus transactions. In reference to memory bus accesses, a posted write is referred to as a posted memory write (PMW).

Worked examples

Example 1 — a first encounter with Posted write

Start with the simplest possible case. Write down what Posted write claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Posted write before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Posted write ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Posted write

In research: Posted write appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Posted write in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Posted write is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer buses, Digital electronics, Motherboard, so understanding it makes those chapters shorter.
In everyday life: Look for Posted write outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Posted write in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Posted write means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Posted write out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Posted write in simple terms?

Why does Posted write matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Posted write?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Posted write.