Transputer

The account begins with binary arithmetic, moves on to on-off (flip-flop) electronic switches, then to serial and parallel processing, and finally to computers/transputers. 

This chapter briefly discusses the advantages to be gained from the use of transputers in acquiring and processing data from an instrument like a mass spectrometer, which routinely deals with large-scale input and output at high speed. 

In contrast with Figure 43.1, there are two transputers, each dealing with a set of instructions. If the processing time for each is 1 msec, the total time required is still about 1 msec. Communication links are needed between the transputers. 

Parallel processing of information is a technique that speeds computer operations without the need to push the limits of existing technology by attempting to build increasingly faster processors. A typical outline of transputer architecture compared with that of a standard computer is shown m Figure 43.3. 

Because the transputer has a 32-bit processor and fast access to considerable quantities of on-chip RAM, it has been called a computer on a chip. Transputers are inherently faster than microprocessors, which have to refer to RAM outside the chip on which they reside. Thus the 100-nsec cycle time used in the above illustration may be only 50 nsec when carried out on the transputer chip. 

A typical transputer architecture. The transputer (sometimes referred to as a computer on a chip) has four input/output links (0, 1, 2, 3) to other transputers, a channel for inputting/requesting data (event link), some built-in random-access memory, an interface to the main operating system (clock, boot, etc.), and an external memory interface. Internal communication is via a bus. 

This big increase in speed has not been without cost. The everyday machine codes and high-level languages (Fortran, Pascal, C, etc.) used to control operations in a standard computer are inappropriate for parallel processing, which needs its own instruction set and has led to the development of special languages for use with the transputer. 

The transputer s advantage in speed relative to common computer operations has also been boosted by reducing the number of basic instruction sets available to the programmer. This aspect is discussed next. 

Microprocessors (transputers), with the help of a special language (Occam), can handle flows of information in a parallel fashion instead of sequentially (serially), thereby greatly increasing the speed of operation. Transputers also control the flow of information by communicating with each other. 

A brief outline of the workings of computers and transputers has been presented in Parts A and B of this discussion (see Chapters 42 and 43), and both should be read before reading this chapter unless the reader is already familiar with the basics of computing. Additional details on some of the functions discussed here are available in other chapters of this book, and cross-references are given where relevant. 

When a mass spectrum has been acquired by the spectrometer/computer system, it is already in digital form as m/z values versus peak heights (ion abundances), and it is a simple matter for the computer to compare each spectrum in the library with that of the unknown until it finds a match. The shortened search is carried out first, and the computer reports the best fits or matches between the unknown and spectra in the library. A search of even 60,000 to 70,000 spectra takes only a few seconds, particularly if transputers are used, thus saving the operator a great deal of time. Even a partial match can be valuable because, although the required structure may not have been found in the library, it is more than likely that some of the library compounds will have stractural pieces that can be recognized from a partial fit and so provide information on at least part of the structure of the unknown. 

Computers, often combined with transputers, are used for three main functions when connected to a mass spectrometer. The foremost requirements involve the acquisition and preprocessing of basic data and the control of the instrument s scanning operations. Additional software programs are available to manipulate the preprocessed data in a wide variety of ways depending on what is required, e.g., a mass spectrum or a total ion chromatogram. 

Chapter 42 Computers and Transputers in Mass Spectrometers, Part A... 

Parallel processing is inherently faster than serial processing, but special processors are needed, and these are called transputers. 

Parallel processing requires that each transputer be able to communicate efficiently with others (up to four immediate neighbors with current transputers) if the final result is not to be garbled. 

Each transputer is a microprocessor with its own memory banks and its own built-in operating mode similar to a conventional microprocessor, but a transputer has additional input and output channels enabling it to communicate with other transputers. For example, in one simple mode, five transputers could be coupled so that four of them were carrying out operations at the same time (in parallel) but controlled by the fifth. 

A special computer language (Occam) is needed to enable transputers to be programmed in this cooperative mode, yielding true parallel processing of information with all its advantages in speed. 

Parallel processing and the RISC set give transputers a considerable speed advantage over conventional serial processors for handling information or flows of data. 

Powerful mass spectrometer/computer systems can achieve simultaneous foreground/background operation, especially if transputers are used to provide the advantage of parallel processing. 

A computer attached to a mass spectrometer is used both to acquire data and to control the operation of the spectrometer. Powerful transputer systems can be used to ensure that both modes of operation can be carried out almost simultaneously. 

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