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Questions tagged [intel]

Retrocomputing hardware and software created by Intel.

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102 votes
6 answers
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Were there 8086 coprocessors other than the 8087?

The 8087 math coprocessor for the 8086 (and descendants) nominally added floating point and transcendental (trigonometric and logarithmic) instructions to the 8086. Contrary to naive expectations, the ...
Euro Micelli's user avatar
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92 votes
10 answers
34k views

How much better was DEC Alpha than contemporaneous x86?

The DEC Alpha, released in 1992, seems like an early implementation of a fully 64-bit microprocessor architecture. Its release led to quite a bit of both marketing hype and genuine vendor support in ...
Brian H's user avatar
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74 votes
8 answers
25k views

Which Linux or BSD distributions do still support i386, i486 or i586 CPUs?

Unfortunately Debian kicked out Pentium 1 (i586) CPU support from its 32-bit PC port (named i386 for historic circumstances) for its next stable release Debian 9 Stretch. (Then again they complain ...
Axel Beckert's user avatar
49 votes
2 answers
4k views

Did Windows NT 4 emulate x86 on non-Intel platforms?

I've been trying to find more information about non-Intel versions of Windows NT regarding x86 emulation but found very little about it. There is one sentence about it in the Wikipedia page but the ...
aybe's user avatar
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48 votes
3 answers
9k views

What's the relationship between early 90s Pentium microprocessor and today's Intel designs?

My simplified understanding of the evolution of the Intel processors over the last 20 years is that the Pentium II and Pentium III architectures were sort of "dead-ends", and today's Intel processors ...
Brian H's user avatar
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41 votes
4 answers
14k views

Is it true that Pentium III was faster than its successor Pentium 4?

My friend told me that earlier iterations of the Pentium 4 were not as fast as the Pentium III, but he didn't have sources. Is it true that the Pentium III was faster than its successor Pentium 4?
May Teresa's user avatar
41 votes
3 answers
6k views

80286 can switch from real mode to protected mode - but why not back?

It's been a while, but I've read in a system programming book that you could switch your Intel 80286 CPU from the normal real mode to a more powerful protected mode. I clearly remember that they said ...
Byte Commander's user avatar
33 votes
4 answers
10k views

Intel CPU bug in the 90s

My teacher who teaches "Logic" at the university told us a story about Intel processors, which goes: "In the 90s, Intel had a bug in the calculation of mathematical functions like sine ...
gomd's user avatar
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31 votes
10 answers
12k views

Should 486s have a heatsink?

I'm building a 486 computer. I plan on using a 100 MHz 486-DX4 that I have which I believe is about as fast as 486's went. The motherboard I will use (Socket 3) appears to support putting a heatsink ...
cbmeeks's user avatar
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30 votes
5 answers
9k views

Are MS-DOS and Windows 9x vulnerable to Meltdown?

In an interesting crossover between current events and Retrocomputing, the vulnerability known as "Meltdown" was publicly disclosed on January 3rd 2018. The retro-computing tie-in is that this ...
Brian H's user avatar
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29 votes
3 answers
7k views

Why did Intel abandon unified CPU cache?

When Intel introduced the 80486 in 1989, they included their first on-chip cache, ostensibly to compete better with Motorola, who had been including on-chip caches for 5 years (MC68020, 1984). Unlike ...
Brian H's user avatar
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28 votes
14 answers
6k views

Were people building CPUs out of TTL logic prior to the 4004, 8080 and the 6800?

I've just finished reading Charles Petzold's book, Code: The Hidden Language of Computer Hardware and Software. In it Charles explains building relays into gates, gates into logic components, and ...
hawkeye's user avatar
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28 votes
2 answers
9k views

The start of x86: Intel 8080 vs Intel 8086?

Why is it said that all modern Intel processors of the x86 family are said to descend from the Intel 8086 and not the Intel 8080? From the Wikipedia article on the Intel 8086, The 8086 gave rise to ...
Evan Carroll's user avatar
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28 votes
3 answers
4k views

Why are the Intel 8080's rotate instructions called opposite to intuition?

The Intel 8080 has two pairs of instructions for rotating the value of the accumulator -- RLC/RRC and RAL/RAR. One of them shifts the 8 bits in the accumulator circularly, writing out into the carry ...
Danya02's user avatar
  • 383
25 votes
3 answers
885 views

Why was segment register value scaled by such a small factor of 16 on i8086?

In 8086 architecture memory is addressed by segment:offset scheme, where the 20-bit linear address is formed as address=segment*16+offset. This looks needlessly complicated and doesn't allow to ...
Ruslan's user avatar
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24 votes
2 answers
7k views

What was the last x86 CPU that did not have the x87 floating-point unit built in?

This Wikipedia page says the following: Most x86 processors since the Intel 80486 have had these x87 instructions implemented in the main CPU So the above quote implies that some CPUs that were ...
user12280's user avatar
  • 293
21 votes
5 answers
3k views

How and why did Intel make the PCI bus "CPU Agnostic"?

Intel invented the original 32/64-bit PCI bus in the early 1990s to replace the decade old ISA bus used in PC's. It was immediately popular (in comparison to Micro Channel or EISA), being both faster ...
Brian H's user avatar
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21 votes
2 answers
8k views

Why did Socket 3 have more pins than needed for the 486?

Intel's Socket 3, used for 486 processors, was a 19×19 pin grid array socket. However, all compatible processors, to my knowledge, used 17×17 PGA packages. What was the point of the extra pins around ...
Hearth's user avatar
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20 votes
2 answers
4k views

Did any notable product use Intel's first RAM?

The 3101 SRAM was Intel's first product. At $99.50 for 64 bits, it had enough memory to store the characters expensiv. (Sorry, the final e costs extra.) Is there a record of any product using it?
DrSheldon's user avatar
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19 votes
2 answers
4k views

What are these weird long ISA slots on this 386 board? (not VLB)

In this image, you can see, from the right, a 16-bit ISA slot (occupied by a controller card), an 8-bit ISA slot, four more 16-bit ISA slots, and two of these strange slots that look like a 16-bit ISA ...
robbie's user avatar
  • 321
19 votes
2 answers
3k views

How did AMD's 386 and 486 perform like Intel's newer generation?

AMD really started to come into its own as a competitor to Intel around the time of the Intel 80486 introduction. AMD countered Intel by shipping the popular (at least with PC enthusiasts) Am386-40, ...
Brian H's user avatar
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18 votes
5 answers
3k views

Was there ever a genuine "mainframe-on-a-chip" microprocessor?

In the 1980s and 90s, there was a fad among the IT industry press to dub the newest "hot" microprocessor on the market as being a "mainframe-on-a-chip". I have seen this fawning description applied to ...
Brian H's user avatar
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18 votes
3 answers
2k views

When did the 386 overtake the 286?

The Intel 80386 was released in 1985, but was initially expensive, and took a long time to fully displace the earlier 80286 from the market; subjectively, I remember significant numbers of 286 ...
rwallace's user avatar
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18 votes
1 answer
1k views

Why is the 8254's default rate 18.2 Hz?

The Intel 8253/8254 timer, in its default configuration, triggers IRQ0 18.2 times per second. Why this strange rate, and not something like 60 Hz (to match the most common video refresh rate) or 100 ...
Mark's user avatar
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18 votes
1 answer
3k views

Which undocumented 8085 instructions is Steven Morse referring to in "In The Beginning"?

In S. P. Morse's 1980 allegory, "In The Beginning", he writes And Intel said, "Let there be an 8085 with an oscillator on the same chip as the processor, and let an on-chip system controller ...
Evan Carroll's user avatar
  • 3,388
17 votes
2 answers
1k views

Which computers used the Intel 82786 graphics chips, and what sort of commercial success did that chip attain?

In the late 1980's, Intel offered the 82786 graphics chip, with specific support for windowed environments. I remember it being covered in Byte magazine, but don't remember seeing any applications of ...
mschaef's user avatar
  • 4,836
15 votes
1 answer
3k views

What's the story behind the "mysterious" 486DX3?

As I was skimming through an old MS-DOS game's README, I stumbled upon this: Therefore, we reccomend a newer 486-100 or better, preferably with a large external cache. Best performance will result ...
aybe's user avatar
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15 votes
1 answer
2k views

What is the history of the Intel 8275 video controller?

The highly popular at the time build-it-yourself home computer Radio 86RK, designed in the Soviet Union, contained a rather mysterious video controller chip КР580ВГ75. It had a high end, feature rich ...
h22's user avatar
  • 413
14 votes
4 answers
11k views

How do I run PowerPC Applications on an Intel Mac

Apple created a dynamic binary translator called Rosetta and bundled it into their OS X operating system. As of OS 10.7, however, Rosetta was removed, and PowerPC applications are no longer supported ...
JAL's user avatar
  • 9,620
14 votes
1 answer
1k views

Intel "Kernel processor" or "OS Kernel"

I used to have an Intel data book from 1981. I gave it away to a friend, and he probably also lost it along the way. In this book there was a data sheet for a component called "OS Kernel" or ...
chthon's user avatar
  • 700
14 votes
1 answer
703 views

SYSENTER/SYSEXIT broken on Pentium Pro and Pentium II?

I was just reading What is linux-gate.so.1?, and it says this: Intel recognized this problem early on and introduced a more efficient system call interface in the form of sysenter and sysexit ...
Evan Carroll's user avatar
  • 3,388
13 votes
1 answer
2k views

Intel processor transistor type evolution

The Intel 4004 used MOS (metal–oxide–semiconductor) transistors. What has been the transistor types used in Intel processors onwards from the 4004 to 8085 to the x86 family of instruction set ...
Single Malt's user avatar
  • 1,859
13 votes
3 answers
522 views

How much extra die area did a CMOS CPU take?

Starting in the late seventies, the microchip industry generally switched from NMOS to CMOS, primarily because CMOS circuits use less power, though they also have other advantages like more noise ...
rwallace's user avatar
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12 votes
1 answer
2k views

Which endian was the Intel 4004?

The Intel 4004 had 4-bit buses and data words, but the program counter and code address space was 12 bits. Was the 4004 little endian (like all of Intel's later microprocessors and microcontrollers) ...
DrSheldon's user avatar
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11 votes
2 answers
2k views

When specifying Intel 80x86 instruction execution time, what is included in the cycle count?

I'm looking at this summary of the Intel x86 integer instruction set (though the same data seems to have been published in a number of places), which gives instruction timings on a per-instruction-...
user's user avatar
  • 5,326
10 votes
2 answers
2k views

First x86 Software Development Manual

These manuals are now called “Intel® 64 and IA-32 Architectures Software Developer Manuals”, and the current version is 71. What was the original name of this manual and when was it released?
Single Malt's user avatar
  • 1,859
10 votes
2 answers
818 views

8086 pinout and address space limit

It is tempting to say - and I have said - that Intel made a mistake in the design of the 8086 and 8088, in going from 16 bit addresses to only 20 bits; if they had even shifted the segment registers ...
rwallace's user avatar
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9 votes
3 answers
2k views

Intel 8080 - Behaviour of the carry bit when comparing a value with 0

I'm in the process of writing an emulator for the Intel 8080. The description of the CMP instruction from Intel's 8080 programming manual (see page 20) says the following: The specified byte is ...
linuxuser's user avatar
9 votes
1 answer
378 views

What was the 6-bit length instruction(s) in the Intel iAPX 432?

The iAPX 432 was arguably the most complex processor architecture ever and a commercial failure for Intel. It was a stack machine with no visible general-purpose registers. It had hardware support ...
DrSheldon's user avatar
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9 votes
1 answer
791 views

Is there any reason to chose ES, FS, or GS over the others in real mode?

The Wikipedia page on X86 Memory Segmentation says In real mode, the registers CS, DS, SS, and ES point to the currently used program code segment (CS), the current data segment (DS), the current ...
Evan Carroll's user avatar
  • 3,388
9 votes
2 answers
365 views

What floating point libraries were written to meet the IEEE 754 standard before it was accepted in 1985?

The IEEE 754 floating point arithmetic working group began in 1977 and was formally accepted in 1985. One of the original driving factors of the standard itself was Intel who wanted a standard to go ...
Adam Hyland's user avatar
8 votes
3 answers
2k views

Why was the size of the 1989 Intel i860 (aka 80860) memory bus 64bit?

On Wikipedia I have read the i860 from 1989 memory bus was at least 64bits wide. (It is the first CPU the Windows NT kernel was running on.) I think even 10 years later (1999) most desktop CPUs were ...
zomega's user avatar
  • 5,372
8 votes
2 answers
1k views

Intel 8080 Read/Set Interrupt Mask Instructions

According to Intel's 8080-8085 Assembly Language Programming guide, the OP Code 20 corresponds to the Read Interrupt Mask (RIM) instruction, and 30 corresponds to the Set Interrupt Mask (SIM) ...
JAL's user avatar
  • 9,620
8 votes
2 answers
1k views

When did Intel undergo the SEX change?

I am reading the book "The 8086 / 8088 Primer Second Edition" by Stephen P Morse. In it on page 54, it says The 8086 provides instructions to facilitate the task of sign extension. These ...
Evan Carroll's user avatar
  • 3,388
8 votes
0 answers
312 views

Undefined opcodes for the Intel 8008 CPU

What happens when I8008 CPU reads the "undefined" opcode (22h, 2Ah, 32h, 38h, 39h, 3Ah; or in octal 042, 052, 062, 070, 071, and 072)? Are these opcodes evaluated as a NOP instruction, or ...
Martin Maly's user avatar
  • 5,575
7 votes
1 answer
1k views

What was the first Intel x86 processor with "Base + Index * Scale + Displacement" addressing mode?

As the title says, what's the first x86 processor from Intel that supports the following addressing mode? mov %reg, 8(base, index, 4) ^^^^^^^^^^^^^^^^^ where the content of %reg will be ...
iBug's user avatar
  • 199
7 votes
1 answer
655 views

80387 transistor count

In 1985, Intel released the 80386, a particularly complex and sophisticated microprocessor for its day, consisting of 275,000 transistors, a rather large number for the day. How many transistors went ...
rwallace's user avatar
  • 62.4k
7 votes
0 answers
88 views

iRMX bootsector on a iRMX partition how to clone?

I have an old year 2000 instrument which has a 340MB hard drive. I am trying to clone the hard drive but I am having major issues. First the instrument uses iRMX and MSDOS the bios is using the CHS ...
mpcengineer's user avatar
7 votes
0 answers
400 views

How was the Intel 80486 debugged? [closed]

How was the Intel 80486 (from 1989) debugged? I'm assuming it was written in some HDL language, like Verilog. However, how was testing and debugging of the CPU carried out? Were there several steps ...
AlphaCentauri's user avatar
6 votes
3 answers
3k views

LCD Displays with the Intel 8080

A colleague of mine mentioned that in college he wrote a slot machine program on an Intel 8080 using an LCD display. What kind of display communication protocol existed on the Intel 8080? How was ...
JAL's user avatar
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