8087 coprocessor

Intel 8087 is a numeric co-processor for Intel 8086, 8088, 80186 and 80188 processors. The 8087 has 8 80-bit general registers implemented as a stack. All floating point operations are performed with data from the stack (usually the data at the top of the stack) and data from external memory. Effective address calculation for external memory accesses is performed by the main processor. Both the main processor and the 8087 decode floating-point instructions (they all start from ESCAPE bit pattern). If the decoded instruction references the memory then the main processor calculates memory effective address and performs "dummy read" of memory. The Intel 8087 captures the memory address and, possibly, data, and uses the captured address to read more data or write data to memory. After that the main processor may continue to execute integer instructions without waiting until the 8087 completes execution of the FP instruction. To synchronize execution of multiple FP instructions the main processor used WAIT (FWAIT) instruction to wait until the co-processor becomes available. Because the integer instructions and floating-point instructions could be executed in parallel, it was common to see integer and FP instructions intermixed in x86 programs.

Intel 8087 co-processor supports integer, BCD, single and double precision floating-point numbers, as well as extended precision (80-bit) floating-point numbers. When the 8087 loads data from memory it always converts it internally to extended-precision number, and all further calculations are performed with this number. This is why switching from double to single-precision number or from 64-bit integer to 32-bit or 16-bit integer numbers doesn't provide any significant performance boost.

Intel was not the only manufacturer of this co-processor. AMD and Cyrix Corporation both produced 8087 co-processors. Soviet Union produced clones of 8087 FPU. There are 8087 co-processors stamped "IBM", but it seems that IBM Corporation didn't manufacture the chips and only re-branded Intel chips.

80186 and 80188 Processors

After Intel produced the 8086 and 8088 chips, it turned its sights toward producing a more powerful chip with an increased instruction set. The company's first efforts along this line—the 80186 and 80188—were unsuccessful. But incorporating system components into the CPU chip was an important idea for Intel because it led to faster, better chips, such as the 286.

The relationship between the 80186 and 80188 is the same as that of the 8086 and 8088; one is a slightly more advanced version of the other. Compared CPU to CPU, the 80186 is almost the same as the 8088 and has a full 16-bit design. The 80188 (like the 8088) is a hybrid chip that compromises the 16-bit design with an 8-bit external communications interface. The advantage of the 80186 and 80188 is that they combine on a single chip 15 to 20 of the 8086–8088 series system components—a fact that can greatly reduce the number of components in a computer design. The 80186 and 80188 chips were used for highly intelligent peripheral adapter cards of that age, such as network adapters.

8088 and 8086 Processors

Intel introduced a revolutionary new processor called the 8086 back in June of 1978. The 8086 was one of the first 16-bit processor chips on the market; at the time virtually all other processors were 8-bit designs. The 8086 had 16-bit internal registers and could run a new class of software using 16-bit instructions. It also had a 16-bit external data path, which meant it could transfer data to memory 16 bits at a time.

The address bus was 20 bits wide, meaning that the 8086 could address a full 1MB (2²⁰) of memory. This was in stark contrast to most other chips of that time that had 8-bit internal registers, an 8-bit external data bus, and a 16-bit address bus allowing a maximum of only 64KB of RAM (2¹⁶).

Unfortunately, most of the personal computer world at the time was using 8-bit processors, which ran 8-bit CP/M (Control Program for Microprocessors) operating systems and software. The board and circuit designs at the time were largely 8-bit as well. Building a full 16-bit motherboard and memory system would be costly, pricing such a computer out of the market.

The cost was high because the 8086 needed a 16-bit data bus rather than a less expensive 8-bit bus. Systems available at that time were 8-bit, and slow sales of the 8086 indicated to Intel that people weren't willing to pay for the extra performance of the full 16-bit design. In response, Intel introduced a kind of crippled version of the 8086, called the 8088. The 8088 essentially deleted 8 of the 16 bits on the data bus, making the 8088 an 8-bit chip as far as data input and output were concerned. However, because it retained the full 16-bit internal registers and the 20-bit address bus, the 8088 ran 16-bit software and was capable of addressing a full 1MB of RAM.

For these reasons, IBM selected the 8-bit 8088 chip for the original IBM PC. Years later, IBM was criticized for using the 8-bit 8088 instead of the 16-bit 8086. In retrospect, it was a very wise decision. IBM even covered up the physical design in its ads, which at the time indicated its new PC had a "high-speed 16-bit microprocessor." IBM could say that because the 8088 still ran the same powerful 16-bit software the 8086 ran, just a little more slowly. In fact, programmers universally thought of the 8088 as a 16-bit chip because there was virtually no way a program could distinguish an 8088 from an 8086. This allowed IBM to deliver a PC capable of running a new generation of 16-bit software, while retaining a much less expensive 8-bit design for the hardware. Because of this, the IBM PC was actually priced less at its introduction than the most popular PC of the time, the Apple II. For the trivia buffs out there, the IBM PC listed for $1,265 and included only 16KB of RAM, while a similarly configured Apple II cost $1,355.

The original IBM PC used the Intel 8088. The 8088 was introduced in June 1979, but the IBM PC did not appear until August 1981. Back then, there was often a significant lag time between the introduction of a new processor and systems that incorporated it. That is unlike today, when new processors and systems using them are often released on the same day.

The 8088 in the IBM PC ran at 4.77MHz, or 4,770,000 cycles (essentially computer heartbeats) per second. Each cycle represents a unit of time to the system, with different instructions or operations requiring one or more cycles to complete. The average instruction on the 8088 took 12 cycles to complete.

Computer users sometimes wonder why a 640KB conventional-memory barrier exists if the 8088 chip can address 1MB of memory. The conventional-memory barrier exists because IBM reserved 384KB of the upper portion of the 1,024KB (1MB) address space of the 8088 for use by adapter cards and system BIOS. The lower 640KB is the conventional memory in which DOS and software applications execute.

about the designer of 4004

The 4004, the world's first microprocessor, is signed with the initials F.F., for Federico Faggin, its designer. Signing the chip was a spontaneous gesture of proud authorship. It was also an original idea, imitated after him by others. Faggin initially etched the F.F. inside the design. Later he moved them to its border, like the autograph on a work of art. The signature is a particularly poignant testimony because, at the time of its birth, the first microprocessor, far from being considered a milestone by Intel's management, represented a diversion from the mainline business of the company which was memory chips.

The birth of the 4004 was an intense moment witnessed by Faggin alone, working into the night in the deserted Intel labs. He had received the 4004 wafers from the manufacturing line at around 6 PM, in January 1971, as people were leaving for the day. With hands trembling and heart pounding he loaded the wafers in the wafer prober and connected it to the tester. A sigh of relief raised from his chest, above the humming of the instruments, as he observed electrical activity in the device. As the testing progressed, the tension was gradually transforming into elation as all the critical functions showed to be operating properly. At around 3 AM, exhausted and ecstatic, Faggin left the lab. At home his wife, Elvia, was waiting for the news. "It works"! he announced, and they shared the happiness in this moment of triumph.

Federico Faggin signed the 4004 because:

• He was the leader of the design/development project of the first microprocessor, and brought it to its successful conclusion.



• Faggin did the detailed design work (logic design, circuit design, chip layout, tester design and test program development) with help from Masatoshi Shima, a Busicom software and logic designer without any previous chip design experience.



• Busicom presented to Faggin the engineering prototype of their calculator with the first 4004. Faggin in 1996 donated it to the Computer History Museum in Silicon Valley.



• He was the original developer of the Silicon Gate Technology, the first commercial self-aligned gate process, and the designer of the world's first commercial integrated circuit using the silicon gate technology: the Fairchild 3708. This semiconductor technology was copied by Intel and made into its core manufacturing technology, enabling the early realization of high-performance memories and the microprocessor.



• Faggin made two other key inventions at Fairchild: the Buried Contact and the Bootstrap Load. At Intel he applied these innovations to build the first microprocessor. They were essential in making the 4004 a reality with the technology available in 1970. Faggin also created the basic Methodology of Random Logic Design using silicon gate technology. This methodology did not exist at Intel or anywhere else until he developed it in 1970. It set the style of design used for all early generations of microprocessors at Intel.
  He also created a very innovative layout and invented many special circuits, for example: a static MOS shift register, a new type of counter and a new automatic power-on reset circuit (US patent 3,753,011).



• He demostrated that the 4004 could be used for applications other than calculators and vigorously campaigned inside Intel to make the 4004 available to the general market.



• Two patents cover Intel's first microprocessor: patent no. 3,821,715, Memory System for a Multi-Chip Digital Computer, in the names of Ted Hoff, Stan Mazor and Federico Faggin; and patent no. 3,753,011, power supply settable, bi-stable circuit, in the name of Federico Faggin.

intel's 4004

Intel's First Microprocessor—the Intel® 4004

Intel® 4004 microprocessor In 2006, Intel marked the 35th anniversary of one of the most significant products in technology history. The Intel® 4004 microprocessor, introduced in November 1971, started an electronics revolution that changed our world. There were no customer-programmable microprocessors on the market before the 4004. It was the first and it was the enabling technology that propelled software into the limelight as a key player in the world of digital electronics design.

Revolutionizing the world of electronics

Busicom* 141-PF printing calculator In 1969 Nippon Calculating Machine Corporation requested Intel design 12 custom chips for its new Busicom* 141-PF printing calculator. Instead of creating a dozen custom chips specifically for the calculator, Engineers Marcian E. "Ted" Hoff, Federico Faggin, and Stanley Mazor, co-inventors of the Intel 4004. Intel's engineers proposed a new design: a family of just four chips, including one that could be programmed for use in a variety of products. MCS-4 Engineers Marcian E. "Ted" Hoff, Federico Faggin, and Stan Mazor came up with a design that involved a set of four chips called the MCS-4. They included a central processing unit (CPU) chip—the 4004, a supporting read-only memory (ROM) chip for the custom applications programs, a random access memory (RAM) chip for processing data, and a shift register chip for input/output (I/O) port. Intel delivered the four chips, and Busicom eventually sold some 100,000 calculators.

Intel introduces the Intel 4004 microprocessor

Intel offered Busicom a lower price for the chips in return for securing the rights to the microprocessor design and the rights to market it for non-calculator applications. Busicom, in financial trouble, agreed.

The Intel ad in the November 15, 1971 issue of Electronic News introduced the Intel 4004 microprocessor and declared "Announcing a new era of integrated electronics." That programmable chip, the Intel 4004, became the first general-purpose microprocessor on the market—a "building block" that engineers could purchase and then customize with software to perform different functions in a wide variety of electronic devices.