computer science

Xputer

Xputer 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 Xputer rather than just read about it. In short: The Xputer is a design for a reconfigurable computer, proposed by computer scientist Reiner Hartenstein. Hartenstein uses various terms to describe the various innovations in the design, including config-ware, flow-ware, morph-ware, and "anti-machine".

Key takeaways

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

Reference excerpt

The Xputer is a design for a reconfigurable computer, proposed by computer scientist Reiner Hartenstein. Hartenstein uses various terms to describe the various innovations in the design, including config-ware, flow-ware, morph-ware, and "anti-machine". The Xputer represents a move away from the traditional von Neumann computer architecture, to a coarse-grained "soft arithmetic logic unit (ALU)" architecture. Parallelism is achieved by configurable elements known as reconfigurable datapath arrays (rDPA), organized in a two-dimensional array of ALU's similar to the KressArray.

Architecture The Xputer architecture is data-stream-based and is the counterpart of the instruction-based von Neumann computer architecture. The Xputer architecture was one of the first coarse-grained reconfigurable architectures, and consists of a reconfigurable datapath array (rDPA) organized as a two-dimensional array of ALUs (rDPU). The bus-width between ALU's were 32-bit in the first version of the Xputer. The ALUs (also known as rDPUs) are used for computing a single mathematical operation, such as addition, subtraction or multiplication, and can also be used purely for routing. ALUs are mesh-connected via three types of connections, and dataflow along these connections are managed by an address generation unit.

Nearest neighbour (connections between neighbouring ALUs) Row/column back-buses Global bus (a single global bus for interconnection between further ALUs) Programs for the Xputer are written in the C language, and compiled for usage on the Xputer using the CoDeX compiler written by the author. The CoDeX compiler maps suitable portions of the C program onto the Xputer's rDPA fabric. The remainder of the program is executed on the host system, such as a personal computer.

rDPA A reconfigurable datapath array (rDPA) is a semiconductor device containing reconfigurable data path units and programmable interconnects, first proposed by Rainer Kress in 1993, at the University of Kaiserslautern. Instead of FPGAs (field-programmable gate arrays) having single bit configurable logic blocks (CLBs), rDPAs have multiple bits wide (for instance, 32-bit path width) reconfigurable datapath units (rDPUs). Each rDPU can be configured to perform an individual function. These rDPUs and interconnects can be programmed after the manufacturing process by the customer/designer (hence the term "reconfigurable") so that the rDPA can perform whatever complex computation is needed. Because rDPUs are multiple bits wide (for instance, 32 bits), we talk about coarse-grained reconfigurability - in contrast to FPGAs with single-bit wide configurable logic blocks, called fine-gained reconfigurable. rDPAs are structurally programmed from "config-ware" source code, compiled into pipe-networks to be mapped onto the rDPA. rDPAs are not instruction-stream-driven and have no instruction fetch at run time. rDPUs do not have a program counter.

References

Worked examples

Example 1 — a first encounter with Xputer

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

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

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

Frequently asked questions

What is Xputer in simple terms?

Why does Xputer 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 Xputer?

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 Xputer.