Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
REPORT ON MINI COMPUTERS PRESENTED TO PROF.ADNAN KHALID PRESENTED BY NIDA IRFAN L1F10BBAM0452 AHSAN AKRAM L1F10BBAM0003 USMAN BASHIR L1F10BBAM0101 AMBER SHAHEEN L1S10BBAM0053 GHULAM HASSAN L1F10BBAM0277 Mini computers Minicomputers are computers that are somewhere in between a microcomputer and a main frame computer. In times past, the minicomputer was typically a standalone device that was ideal for use by small and mid-sized businesses who needed more power and memory than could be obtained with microcomputers, but did not have a need for the resources provided by mainframes. More recently, a minicomputer is thought of in terms of being a server that is part of a larger network. In the early years of computer technology, a hierarchy of computer sizes and types was used to define the level of operation needed for different types of applications. The levels ranged from the embedded systems that functioned more or less automatically to parallel processing systems that was capable of supporting a huge network of interconnected computers and performing a wide array of tasks simultaneously. The minicomputer tended to be somewhat low on the hierarchical listing, in that the device was considered to be limited in ability. The original structure for a minicomputer was a simple computer system that was equipped with essential programs and functions that would handle simple tasks, such as word processing. The minicomputer was equipped with terminals that made it possible to attach peripheral devices to the system, such as a printer. However, the minicomputer usually did not have hardware or software that allowed the device to be integrated into a larger network. However, if there was no need to use comprehensive applications or interact with other systems, the minicomputer was often sufficient. Over time, the concept of a minicomputer has become somewhat obsolete. As technology has continued to evolve, many tasks that was once the exclusive province of the larger and more powerful mainframe computers has been assumed by the workstation computers of today. Still, the mainframe remains in existence, although the purpose and function is often associated with the role of a large server to support a network of workstations. In like manner, the minicomputer has morphed into a server that is ideal for smaller and more localized networks. Minicomputers are used for scientific and engineering computations, business-transaction processing, file handling, and database management, and are often now referred to as small or midsize servers. HISTORY OF Mini COMPUTERS Packard Bell PB250 This was the first machine in the collection. It was built around 1961 and predates true minicomputers, since it was rather slow and at $50,000 for a typical system it was too expensive. Otherwise it is like a mini in that it is small and takes little power. It is a 22-bit serial machine with acoustic delay line memory. The basic IO device was a Friden Flexowriter. DEC PDP-8 Classic Introduced in 1965, this is usually considered the first true minicomputer because it was the first computer for less than $25,000. It was also much faster than earlier machines such as the PB250. Its the key (though not the first) member of Digital's highly successful Data General SuperNOVA Data General was an early competitor to DEC. This fast 16-bit mini had some primitive protection features. Although most of the minicomputers in the collection were made by Digital, I do have this DG and an HP 2100A. DEC PDP-11 The PDP-11 came out in 1970 and gradually displaced the PDP-8 family. It was a 16-bit machine with an elegant instruction set. The collection includes this first model, the PDP-11/20, and the next and more powerful model, the PDP-11/45. Minicomputers pretty much died out when the microprocessor took over. They went upscale to machines like the VAX, which eventually grew to mainframe size. Some minicomputer architectures lived on as microprocessors, the PDP-8 in the Intersil 6100 series chips and the PDP-11 in the LSI-11 processors. Structure of mini computers Minicomputers were built based on integrated circuits (ICs), so-called "chips". This technology of constructing logical gates was invented independently by both Jack Kilby and Robert Noyce in late 1950s. They imprinted circuit networks on isolating material and used semiconductor material - such as silicium or germanium - to take care of the actual logical operations. The advantages of integrated circuits compared to transistors were significant: They were not only smaller and faster, but also more reliable and consumed less power. Furthermore, it was now possible to automate the production of these new chips, which made them more widely available at a considerable lower price. . Presper Eckert, co-inventor of the ENIAC, noted in 1991: "I didn't envision we'd be able to get as many parts on a chip as we finally got." In fact, in 1964 Gordon Moore, who worked as semiconductor engineer by then and went on to co-found Intel four years later, observed that the complexity of integrated circuits doubles every year (Moore's Law). This bold statement held until the late 1970s, at which point the development speed slowed down to double complexity every 18 months. Minicomputer architecture: The DEC PDP-11 Digital Equipment Corporation - DEC for short - was the leader in the market of minicomputers, both financially and technologically speaking. Their most succesful line of products was the PDP series, PDP standing for Programmed Data Processor. As already mentioned, these computers were relatively cheap with prices ranging in the ten-thousands of dollars, this fact making them quite popular amongst universities. Furthermore, they introduced interactive computing, meaning that for the first time the user was given a direct feedback while doing his work. Up until then, programs were usually entered on punch cards and the result of the computation was eventually printed out on other punch cards. The minicomputers used the line printer and later introduced the cathode-ray-tube (CRT) or monitor as a way of giving quick feedback to the user. As multiple terminals (combinations of input and output devices) were attached to the same main unit, a need arose to handle the input, output and processing of all the terminals simultaneously. This is why minicomputers, such as the PDP-11, came equipped with a time-sharing operating system capable of handling multiple task at the same time. The DEC PDP-11 was the successor of the PDP-10 and the predecessor of the VAX-11. Just as the PDP-10 it was delivered with the TOPS-10 (Time-sharing OPerating System) operating system and the MACRO-10 assembler. At the MIT an own operating system called ITS (Incompatible Time-sharing System) was developed. The main hardware features of the PDP-11 were: o o o o o 8 general-purpose registers labeled R0 till R7, with R7 also being used as the program counter 64K memory with a 16 bit address fixed-point integers in two's complement notation both 8 bit (1 byte) and 16 bit (1 word) long floating-point numbers both 32 and 64 bit long external UNIBUS for bi-directional, asynchronous data communication between devices The inner view of DEC PDP-11 Because of the UNIBUS architecture, it was possible to built the components of the PDP-11 in a modular way. This had the additional benefit that the system could be refitted with numerous extensions, thus enhancing its overall capabilities. Below is a list of some of the available extensions: o o o o o o o o Extended Arithmetic Element (EAE) for fixed-point multiply, divide and shift Extended Instruction Set (EIS) enhancing the CPU to perform the operations above using general purpose registers Floating Point Processor (FPP) operating on six associated registers Floating Instruction Set (FIS) using a stack architecture for floating-point operations FASTBUS and high-speed memory connects a high-speed memory between CPU and UNIBUS Cache memory interposed between CPU and main memory Memory management extending the physical address space MASSBUS for high-speed Input/Output 4. Software The most important single piece of software that ran on these machines was, of course, the operating system. Up until the early 1970s operating systems were written in machine specific, tight assembler code. This was considered necessary because only by hand-coding the innermost loops it was possible to achieve the optimal performance of the machine. The drawback of this approach obviously was that the code could not be reused, if another architecture differed in just the slightest way. While IBM did quite a good job at keeping things compatible, DEC wasn't very concerned about this issue. In fact, even within the PDP series the machine designs were quite different, for example the length of a word in memory would vary between 7 and 16 bits as time went on. In 1969 Bell Labs started work on a new kind of operating system which was supposed be called "Multics". Partly based on MIT's ITS, the main goal was to hide the complexity of the computer from programmers as well as users. However, this project was canceled due to disagreements between Bell Labs and their associates. Fortunately, Ken Thompson, who was in the team that first worked on Multics, implemented parts of the project and some of his own ideas on a salvaged PDP-7 using the B programming language. He calls the resulting system "Unix". Roughly at the same time Dennis M. Ritchie develops the C programming language which has some of its roots in B that was used to first implement Unix. During the time from 1972 to 1974 Ken Thompson reimplements Unix in C constantly improving the system. A first version of Unix is presented at a symposium on operating system principles at Purdue University in 1973. The Unix operating system and the C programming language broke with the old principle of system level programming which was supposed only to be done in assembler. This new approach, while not achieving the same performance initially, had another huge advantage: Once the C compiler had been modified to produce machine code for a new architecture, all programs written until then could easily be recompiled and would run on the new platform without major problems. This was impossible to do with assembly code. The concept of making software portable between different platforms eliminated the need to start working from scratch again for each new architecture. Unix, being the first portable operating system, was immensely succesful and already by 1975 it ran on several different platforms including IBM System/370, Honeywell 6000 and Interdata 8/32. Also, it was now possible to easily port common tools to all platforms. Taken together with the standardized interface of system calls through which Unix gives access to the machine, these two factors contributed considerable to making programming much easier than it was ever before. 5. Conclusion The world of computers has dramatically changed during the 1970s. Starting off in the world of the mainframes of the 1950s and 1960s, only 10 years later not only the hardware has changed considerably, also some new concepts have rendered old assumptions obsolete: It now is important that systems are compatible to each other, interactivity is a prerequisite, and as far as software is concerned portability is the new way to go. Yet the 1970s should be considered just a transitional phase. As the technology advances even more rapidly, it becomes obvious that soon enough new ideas will be challenging these assumptions once again. The PC desktop revolution is just around the corner. SOURCES www.piercefuller.com www.inf.fu-berlin.de