computer science

Futurebus

Futurebus 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 Futurebus rather than just read about it. In short: Futurebus (IEEE 896) is a computer bus standard designed to replace all local bus connections in a computer, including the CPU, plug-in cards, and even some LAN links between machines. The project started in 1979 and was completed in 1987, but then went through a redesign until 1994.

Key takeaways

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

Reference excerpt

Futurebus (IEEE 896) is a computer bus standard designed to replace all local bus connections in a computer, including the CPU, plug-in cards, and even some LAN links between machines. The project started in 1979 and was completed in 1987, but then went through a redesign until 1994. It has seen little real-world use, although custom implementations are still designed.

History In the late 1970s, VMEbus was faster than the parts plugged into it. It can connect a CPU and RAM to VME on separate cards to build a computer. However, as the speed of the CPUs and RAM rapidly increased, Futurebus created a successor to VMEbus using asynchronous links. Though the ability to have several cards in the system as "masters", allowing Futurebus to build multiprocessor machines, required some form of "distributed arbitration" to allow the various cards to gain access to the bus at any point, as opposed to VME, which put a single master in slot 0 with overall control. Typical IEEE standards start with a company building a device, then submitting it to the IEEE for the standardization effort. In the case of Futurebus, the whole system was being designed during the standardization effort. It took eight years before the specification was finally agreed on in 1987. Tektronix did make a few workstations based on Futurebus. It took another four years for the Futurebus+ Standard to be released. The IEEE 896 committee later split from the IEEE Microcomputer Standards Committee and formed the IEEE Bus Architecture Standards Committee (BASC). Futurebus+ transceivers that meet the IEEE Standard 1194.1-1991 Backplane Transceiver Logic (BTL) standard are still made by Texas Instruments. Futurebus+ was used as the I/O bus in the DEC 4000 AXP and DEC 10000 AXP systems. Futurebus+ FDDI boards are still supported in the OpenVMS operating system.

See also InfiniBand QuickRing Scalable Coherent Interconnect (SCI) Bus topology FASTBUS

References

Further reading The Futurebus+ Handbook, John Theus, VITA Futurebus+ Handbook for Digital Systems, Digital Equipment Corporation IEEE Standard Backplane Bus Specifications for Multiprocessor Architectures: Futurebus+, IEEE Std 896.1-1987 IEEE Standard for Futurebus+(R) -- Logical Protocol Specification, IEEE Std 896.1-1991 IEEE Standard Backplane Bus Specification for Multiprocessor Architectures: Futurebus+, IEEE Std 896.2-1991

External links Buses at the Wayback Machine (archived February 12, 2010)

Worked examples

Example 1 — a first encounter with Futurebus

Start with the simplest possible case. Write down what Futurebus 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 Futurebus 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 Futurebus 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 Futurebus

In research: Futurebus 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 Futurebus 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: Futurebus is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer buses, IEEE standards, so understanding it makes those chapters shorter.
In everyday life: Look for Futurebus 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 Futurebus in 20 minutes

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

Frequently asked questions

What is Futurebus in simple terms?

Why does Futurebus 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 Futurebus?

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 Futurebus.