A CPU History


Intel 486 (1989 – 1994)


The 80486DX was released in 1989. It was a 32-bit processor containing 1.2 million transistors. It had the same memory capacity as the 386 (both were 32-bit) but offered twice the speed at 26.9 million instructions per second (MIPS) at 33 MHz. There are some improvements here, though, beyond just speed. The 486 was the first to have an integrated floating point unit (FPU) to replace the normally separate math coprocessor (not all flavors of the 486 had this, though). It also contained an integrated 8 KB on-die cache. This increases speed by using the instruction pipelining to predict the next instructions and then storing them in the cache. Then, when the processor needs that data, it pulls it out of the cache rather than using the necessary overhead to access the external memory. Also, the 486 came in 5 volt and 3 volt versions, allowing flexibility for desktops and laptops.


The 486 chip was the first processor from Intel that was designed to be upgradeable. Previous processors were not designed this way, so when the processor became obsolete, the entire motherboard needed to be replaced. With the 486, the same CPU socket could accommodate several different flavors of the 486. Initial 486 offerings were designed to be able to be upgraded using “OverDrive” technology. This means you can insert a chip with a faster internal clock into the existing system. Not all 486 systems could use OverDrive, since it takes a certain type of motherboard to support it.


The first member of the 486 family was the i486DX, but in 1991 they released the 486SX and 486DX/50. Both chips were basically the same, except that the 486SX version had the math coprocessor disabled (yes, it was there, just turned off). The 486SX was, of course, slower than its DX cousin, but the resulting reduced cost and power lent itself to faster sales and movement into the laptop market. The 486DX/50 was simply a 50MHz version of the original 486. The DX could not support future OverDrives while the SX processor could.


In 1992, Intel released the next wave of 486′s making use of OverDrive technology. The first models were the i486DX2/50 and i486DX2/66. The extra “2″ in the names indicate that the normal clock speed of the processor is being effectively doubled using OverDrive, so the 486DX2/50 is a 25MHz chip being doubled to 50MHz. The slower base speed allowed the chip to work with existing motherboard designs, but allowed the chip internally to operate at the increased speed, thereby increasing performance.


Also in 1992, Intel put out the 486SL. It was virtually identical to vintage 486 processors, but it contained 1.4 million transistors. The extra innards were used by its internal power management circuitry, optimizing it for mobile use. From there, Intel released various 486 flavors, mixing SL’s with SX’s and DX’s at a variety of clock speeds. By 1994, they were rounding out their continued development of the 486 family with the DX4 Overdrive processors. While you might think these were 4X clock quadruplers, they were actually 3X triplers, allowing a 33 MHz processor to operate internally at 100 MHz.


AM486DX Series (1994 – 1995)


Intel was not the only manufacturer playing in the sandbox at the time. AMD put out its AM486 series in answer to Intel’s counterpart. AMD released the chip in AM486DX4/75, AM486DX4/100, and AM486DX4/120 versions. It contained on-board cache, power management features, 3-volt operation and SMM mode. This made the chip fitting for mobiles in addition to desktops. The chip found its way into many 486-compatibles.


AMD AM5x86 (1995)


This is the chip that put AMD onto the map as official Intel competition. While I am mentioning it here on the 486 page of the history lesson, it was actually AMD’s competitive response to Intel’s Pentium-class processor. Users of the Intel 486 processor, in order to get Pentium-class performance, had to make use of an expensive OverDrive processor or ditch their motherboard in favor of a true Pentium board. AMD saw an opening here, and the AM5x86 was designed to offer Pentium-class performance while operating on a standard 486 motherboard.. They did this by designing the 5×86 to run at 133MHz by clock-quadrupling a 33 MHz chip. This 33 MHz bus allowed it to work on 486 boards. This speed also allowed it to support the 33 MHz PCI bus. The chip also had 16 KB on-die cache. All of this together, and the 5×86 performed better than a Pentium-75. The chip became the de facto upgrade for 486 users who did not want to ditch their 486-based PCs yet.

Pages: 1 2 3 4 5 6 7 8 9 10 11

Comments

  1. Your Notes are very clear and Excelent. If you can update to current, it is very good.

    Thank you

  2. Your notes have helped me a lot about something i’ve been looking for in the past week.your Your notes are excelent thanx

  3. Just to point out that you state the 80186 never made it into a personal computer, however i owned a 186 system around 1992 that was made my Research Machines.
    Just thought you would like to know.

    • There was also a Tandy / Radio Shack PC that used an 80186. Just one model that didn’t last for more than a year. Their usual black and silver case. I can’t swear that it was 100% compatible with the usual instruction sets that software depended on.

      • Hugh Wyn Griffith says:

        That Tandy 186 was the Tandy 2000 and its graphics were not 100% compatible with Windows much to the distress of users (I was one when I bought my first “almost-PC” in the UK back in the ’90′s). This caused a lot of ill feeling between users and Tandy. The Users Group launched a monthly called “Orphans” and hated Ed Juge (who died recently) the then CEO of Tandy for not providing any support.

        I was amused a few years ago when Googling on Tandy 2000 to pull up a full page advert for it from one of the well known magazines at that time in which Bill Gates lauded it saying how much his programmers depended on it for its performance! Might explain some of Windows problems if they were using a non-conforming PC !

    • u probably have the one that was made in 1990 then that was the 1 that did make it in2 the personal computer as is later stated in there

  4. The 5×86 was not AMD’s answer to the Pentium, the P5 was. The 5×86 was made to offer a greater performance boost to the millions of 486 PC’s out there, as it would work in (almost) any 486 motherboard with a socketed CPU or overdrive socket.

  5. Chris, It doesn’t say it was AMD’s answer. It was their “competitive response to Intel’s Pentium-class processor”
    on a 486 motherboard.

    Also, not mentioned is why Intel went from a number designation to a name title, the number, was actually the stock number. As I was told by a Intel Rep. at a Comdex show (Vegas) ’94-’95. As Intel tried to sue AMD for copy right infringement. Like a fragrance, you can’t CR. the recipe only the name. They lost on the grounds, you can’t copy right a stock number (80486)! So they, Intel started using name designation (Pentium). As well as AMD did the same.

  6. This is great, im supposed to be at work, but im reading this, just spent quite a while reading it. Its very interesting, Thank You

  7. Bill Buchanan says:

    Correction to information provided on the Intel 80186 (1980).
    This Processor was used in one desk top system but the system did not sell well. The company was Tandy and the model was Tandy 2000. There is a very good page at: http://www.old-computers.com/museum/computer.asp?c=1219 covering the processor.

  8. Mick Russom says:

    Acorn’s Master 512 PC had a 10MHz 80186 CPU which ran MS-DOS and GEM. I would say this qualifies it as a “PC” running a 80186 running MS-DOS.

  9. Sandy Jelusic says:

    I have at home an pc desktop powered by an 8088 at 3.5 mhz with turbo mode, black-yellow monitor, 20mb disk and only 5.25” floppy. As for dos I think it’s ibm-dos. Not really certain.

  10. Very knowledgeful. Please update with latest changes.

  11. Really your services are good we like it please keep it up.

  12. chelle-marie says:

    that is great i loved the little joke:

    “The following chips are considered the dinosaurs of the computer world. PC’s based on these processors are the kind that usually sit around in the garage or warehouse collecting dust. They are not of much use anymore, but us geeks don’t like throwing them out because they still work. You know who you are.”

    sounds just like my tech teacher becouse he is always complaining about how things have changed and shows us pictures from back when computers still used tapes and how he used to get paid to change the tapes every two hours for a hospitle

  13. Mary Alice Thauvette says:

    This article was posted 23-Mar-01. That was nine years ago. It is time to update the article. Or, at least change the title of the last section from :1999 – Present” to “1999 – March 2001″

  14. what is the significances of the number like 8086 in the processor

  15. thanks for the notess

Leave a Reply