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28-593: By the time the project had delivered its first implementation, new processors like the Sun SPARC and Intel 486 had surpassed its performance, and development was abandoned in 1988. The Rekursiv project started as an effort to improve the assembly line controls in Linn's factories in Glasgow , Scotland . Their lines were automated using a suite of VAX-11 systems, but these were slow and very difficult to program with

56-406: A & ( ∼ a + 1 ) {\displaystyle a\And (\sim a+1)} , where & {\displaystyle \And } means bitwise operation AND and ∼ {\displaystyle \sim } means bitwise operation NOT on a {\displaystyle a} . For MSb 1 numbering, the value of an unsigned binary integer

84-492: A 40-bit identifier which the Objekt chip hashed and used as a pointer to physical memory. Objekt also handled the mapping of the object memory to hard disk for permanent storage, implementing a virtual memory system. To handle garbage collection , Objekt divided the provided dynamic RAM (main memory) into two halves, using one for new object creation and leaving the other unused. When a new object would require more memory than

112-685: A Rekursiv computer ended up at the bottom of the Forth and Clyde canal in Glasgow. According to a post by a researcher at the University of Strathclyde, while the Rekursiv system was being developed, a new version of the LINGO language was written for the Sun SPARC system which emerged at about this time. It ran twice as fast as the Rekursiv hardware, rendering the effort pointless. Sometime after that

140-456: A series of pointers to the memory locations holding the values. In Rekursiv, the addresses are replaced by 40-bit object IDs pointing to a section of memory allocated by Objekt. The most significant bit (MSB) of the 40-bit pointer was set to 1 if the value was an object identifier, or 0 if it was an untyped binary value. The later was used to store large unformatted data, like the data for a digital image, and could only be used within objects. In

168-426: Is not affected by how the value is stored on the device, such as the value's byte order . Rather, it is a property of the numeric value in binary itself. This is often utilized in programming via bit shifting : A value of 1 << n corresponds to the n bit of a binary integer (with a value of 2 ). In digital steganography , sensitive messages may be concealed by manipulating and storing information in

196-414: Is the convention used to identify the bit positions in a binary number . In computing , the least significant bit ( LSb ) is the bit position in a binary integer representing the binary 1s place of the integer. Similarly, the most significant bit ( MSb ) represents the highest-order place of the binary integer. The LSb is sometimes referred to as the low-order bit or right-most bit , due to

224-400: The two's complement method. The MSb most significant bit has a negative weight in signed integers, in this case -2 = -128. The other bits have positive weights. The lsb ( least significant bit ) has weight 2 =1. The signed value is in this case -128+2 = -126. The expressions most significant bit first and least significant bit at last are indications on the ordering of the sequence of

252-650: The NAM. Simulations suggested that Lisp routines written using this style operated about 20 times faster than a Symbolics Lisp machine . The company also produced similar microcode systems for Smalltalk and Prolog, the later reducing Prolog's complex unification operation to a single opcode. The Rekursiv processor consisted of four gate-array chips named Numerik ( 32-bit ALU ), Logik (instruction sequencer), Objekt (object-oriented memory management unit ) and Klock (processor clock and support logic). The original versions were clocked at 10 MHz. Linn intended to sell

280-426: The Rekursiv chip set to vendors, as well as produce their own workstation using it. Initially, the only product was "HADES", the "Hardware Accelerator for Dynamic Expert Systems", which consisted of a VMEbus card that could be plugged into a Sun-3 or Sun-4 workstation. HADES included the four main chips, 2 MB of 45 nanosecond (22 MHz) SRAM and 5 MB of 100 ns (10 MHz) DRAM. Disk access

308-468: The VAX platform. Tiefenbrun concluded the solution to the performance issue was not to improve the language on the VAX but instead produce an entirely new CPU dedicated specifically to running object programs. In 1984, Tiefenbrun formed the wholly owned subsidiary Linn Smart Computing under the direction of University of Strathclyde professor David Harland and the Rekursiv project was born. The first version of

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336-516: The bit number and a base of 2. The value of an unsigned binary integer is therefore where b i denotes the value of the bit with number i , and N denotes the number of bits in total. When the bit numbering starts at zero for the most significant bit (MSb) the numbering scheme is called MSb 0 . The value of an unsigned binary integer is therefore LSb of a number can be calculated with time complexity of O ( n ) {\displaystyle O(n)} with formula

364-433: The bits in the bytes sent over a wire in a serial transmission protocol or in a stream (e.g. an audio stream). Most significant bit first means that the most significant bit will arrive first: hence e.g. the hexadecimal number 0x12 , 00010010 in binary representation, will arrive as the sequence 0 0 0 1 0 0 1 0 . Least significant bit first means that the least significant bit will arrive first: hence e.g.

392-469: The case of a full object, a further simplification was available to store short fields as values within the pointer itself. This was indicated by setting the second MSB to 0 as well. In this case, the following five bits indicated a type, defined by the program's ISA, which might be "integer" or "string fragment". The actual value of this "compact object" was placed in the lower 32-bits of the pointer. This allowed such simple values to be immediately presented to

420-574: The color. In this diagram, green is represented by its RGB value, both in decimal and in binary. The red box surrounding the last two bits illustrates the least significant bits changed in the binary representation. This table illustrates an example of decimal value of 149 and the location of LSb. In this particular example, the position of unit value (decimal 1 or 0) is located in bit position 0 (n = 0). MSb stands for most significant bit , while LSb stands for least significant bit . This table illustrates an example of an 8 bit signed decimal value using

448-467: The company was shut down. The underlying concept of the Rekursiv platform was to provide a hardware-assisted persistent object store, constantly and invisibly writing the memory state to disk without intervention from the operating system or the user's program. One reviewer described it as "an object-database engine for creating and managing persistent objects". To make such a system work with reasonable performance while running complex programs, Rekursiv

476-460: The convention in positional notation of writing less significant digits further to the right. The MSb is similarly referred to as the high-order bit or left-most bit . In both cases, the LSb and MSb correlate directly to the least significant digit and most significant digit of a decimal integer. Bit indexing correlates to the positional notation of the value in base 2. For this reason, bit index

504-419: The entire system image was periodically written to disk, during which time all of the pointers were re-numbered to be consecutive. The processor's instruction set was stored in a dedicated area of static RAM known as the "control store". It was accessed via a dedicated 16-bit bus, organized as 16,384 words of 128-bits each. A separate "control store map" section of SRAM holds a numbered table of entry points into

532-461: The flexibility that Linn's founder, Ivor Tiefenbrun , desired. By the early 1980s, Tiefenbrun had become convinced that object-oriented programming would offer solutions to these problems. In 1981, Tiefenbrun hired a number of programmers to write a version of the Smalltalk language for the VAX systems, borrowing some syntax from ALGOL . Known as LINGO, the system worked but ran very slowly on

560-433: The least significant bits of an image or a sound file. The user may later recover this information by extracting the least significant bits of the manipulated pixels to recover the original message. This allows the storage or transfer of digital information to remain concealed. [REDACTED] A diagram showing how manipulating the least significant bits of a color can have a very subtle and generally unnoticeable affect on

588-468: The microcoded routines, mapping a 10-bit opcode onto one of 2,048 entities. In a conventional processor, the map would normally be implemented in hardwired logic in the opcode decoder. Opcodes could be parts of objects and stored in the same way that any other data would be using Objekt. For performance reasons, a separate memory bank known as NAM (and NAMARG) reserved 524,288 40-bit words storing 10-bit opcodes and 30-bit arguments. NAM connected directly to

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616-409: The processor via its own bus, making it act more like a cache in modern architectures. In practice, the developer of a programming language would first outline the assembler language they desired, which would be the underlying syntax of the language with up to 2,048 instructions. Commonly used routines, like those found in stdlib in C, would then be coded using that assembler language and written to

644-445: The processor without the need to follow a pointer to the physical location, which saved memory and improved performance. Because the top two bits of the 40-bit pointer were used for status flags, Objekt could only identify 2 objects in total. Since the objects were constantly being garbage collected, many of these values might point to non-existent objects, meaning the system could run out of identifiers in practical use. To address this,

672-414: The same hexadecimal number 0x12 , again 00010010 in binary representation, will arrive as the (reversed) sequence 0 1 0 0 1 0 0 0 . When the bit numbering starts at zero for the least significant bit (LSb) the numbering scheme is called LSb 0 . This bit numbering method has the advantage that for any unsigned number the value of the number can be calculated by using exponentiation with

700-467: The system emerged in 1988. A small number of prototype VMEbus boards, called Hades , comprising these four chips plus 80 MB of RAM were produced. These were intended for installation in a host system such as a Sun-3 workstation . Although the Rekursiv was never fully developed and was not a commercial success, several Hades boards were used in academic research projects in the UK . The last known copy of

728-421: Was designed to allow the programmer to write their own instruction set architecture (ISA) dedicated to the language they were using. The microcode instruction set was stored in static RAM . There was no default ISA, although Linn supplied one for running programs in the C programming language . The system did not provide the analog of a memory address to the programs running on it, instead, objects were given

756-480: Was free in the used portion, Objekt paused the system, copied any object with a valid pointer to it to the unused half of memory, and then switched to make the formerly unused half the active portion. In extremely memory-limited cases, Objekt would first attempt to spool some objects to disk, and if that failed to free up enough room, would use both halves of memory. Objects are composite structures with multiple values within them, which in most systems are implemented as

784-563: Was handled by a program running on the underlying Sun system, which significantly hampered performance. Sun SPARC Too Many Requests If you report this error to the Wikimedia System Administrators, please include the details below. Request from 172.68.168.151 via cp1112 cp1112, Varnish XID 944114262 Upstream caches: cp1112 int Error: 429, Too Many Requests at Thu, 28 Nov 2024 08:06:00 GMT Most significant bit In computing , bit numbering

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