computer science

Western Digital FD1771

Western Digital FD1771 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 Western Digital FD1771 rather than just read about it. In short: The FD1771, sometimes WD1771, is a floppy disk controller chip, the first in a line of floppy disk controllers produced by Western Digital. It uses single density FM encoding introduced in the IBM 3740.

Key takeaways

Western Digital FD1771 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 Western Digital FD1771 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Western Digital FD1771 from memory before moving on to harder problems.

Reference excerpt

The FD1771, sometimes WD1771, is a floppy disk controller chip, the first in a line of floppy disk controllers produced by Western Digital. It uses single density FM encoding introduced in the IBM 3740. Later models in the series added support for MFM encoding and increasingly added onboard circuitry that formerly had to be implemented in external components. Originally packaged as 40-pin dual in-line package (DIP) format, later models moved to a 28-pin format that further lowered implementation costs.

Derivatives The FD1771 was succeeded by many derivatives that were mostly software-compatible:

The FD1781 was designed for double density, but required external modulation and demodulation circuitry, so it could support MFM, M2FM, GCR or other double-density encodings. The FD1791-FD1797 series added internal support for double density (MFM) modulation, compatible with the IBM System/34 disk format. They required an external data separator. The WD1761-WD1767 series were versions of the FD179x series rated for a maximum clock frequency of 1 MHz, resulting in a data rate limit of 125 kbit/s for single density and 250 kbit/s for double density, thus preventing them from being used for 8-in (200 mm) floppy drives or the later "high-density" 5.25-inch (133 mm) or 90 mm floppy drives. These were sold at a lower price point and widely used in home computer floppy drives. The WD2791-WD2797 series added an internal data separator using an analog phase-locked loop, with some external passive components required for the VCO. They took a 1 MHz or 2 MHz clock and were intended for 8-inch (203 mm) and 5.25-inch (133 mm) drives. The WD1770, WD1772, and WD1773 added an internal digital data separator and write precompensator, eliminating the need for external passive components but raising the clock rate requirement to 8 MHz. They supported double density, despite the apparent regression of the part number, and were packaged in 28-pin DIP packages. The WD1772PH02-02 was a version of the chip that Atari fitted to the Atari STE which supported high density (500 kbit/s) operation. After production at WD could not be sustained, Atari decided to license the design and modify it to get high density and extra density (1 MBit/s) operation. The chip was codenamed "Ajax", had the number C302096 and was produced by Toshiba.

Compatible chips

Many compatible chips were available from other vendors:

FD179x series from SMC Microelectronics MB8876A and MB8877A from Fujitsu VL177x series from VLSI Technology. Soviet KR1818WG93 (КР1818ВГ93) was a WD1793 analog These were used in many microcomputers including the TRS-80, Acorn Electron, BBC Master, Atari ST, Acorn Archimedes, and the SAM Coupé, as well as the +D and DISCiPLE disk interfaces for the ZX Spectrum, the Commodore 157x/1581 for the Commodore 64 and the Atari XF551 for the Atari 8-bit computers.

References

Further reading Western Digital Storage Management Produces Handbook - describes the entire line of products.

Illustrations

Worked examples

Example 1 — a first encounter with Western Digital FD1771

Start with the simplest possible case. Write down what Western Digital FD1771 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 Western Digital FD1771 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 Western Digital FD1771 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 Western Digital FD1771

In research: Western Digital FD1771 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 Western Digital FD1771 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: Western Digital FD1771 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Floppy disk computer storage, Integrated circuits, Western Digital products, so understanding it makes those chapters shorter.
In everyday life: Look for Western Digital FD1771 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 Western Digital FD1771 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Western Digital FD1771 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 Western Digital FD1771 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Western Digital FD1771 in simple terms?

Why does Western Digital FD1771 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 Western Digital FD1771?

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 Western Digital FD1771.