Questions tagged [8087]

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13 votes
2 answers
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Intel 80188 & 8087 clock frequency differences

Today I saw that the Intel APX-188/186 User's Manual states that you can use a 8087 as coprocessor for the 80188/186 (as the 80187 is only usable with the 186). But I was wondering about the clock ...
juffma's user avatar
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15 votes
2 answers
3k views

Why did the 8087 need a special socket?

The IBM PC included a coprocessor socket for the 8087 floating-point unit. Logical enough; some customers wanted to use the 8087 to make numeric calculations run faster. But why was the 8087 designed ...
rwallace's user avatar
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3 votes
2 answers
443 views

How did databases use the 8087?

A discussion on programs that used the 8087 mentions several categories I expected, and one I did not: Database programs (dBase IV, FoxBase, Paradox, Revelation) The more I think about it, the more ...
rwallace's user avatar
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3 votes
1 answer
731 views

What were the most common applications of the 8087?

The original IBM PC had a slot for the 8087 floating-point coprocessor. This was a somewhat esoteric feature at the time – previous microcomputers had done all their floating-point in software – but ...
rwallace's user avatar
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9 votes
1 answer
1k views

What was the performance penalty for denormal inputs on 80s-era FPUs?

Some FPUs exhibit as much as an order of magnitude slowdown when given denormal inputs, due to having to trap to microcode to handle them. Did early FPUs of the microprocessor era, exhibit substantial ...
rwallace's user avatar
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6 votes
1 answer
473 views

Which x87 first acquired the ability to flush denormal to zero?

On modern Intel FPUs, you can set a flag to cause all denormals to be automatically flushed to zero. On some workloads, this improves performance. I cannot find any mention of that flag in the data ...
rwallace's user avatar
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17 votes
3 answers
3k views

x87 trigonometric instructions

The 8087 has instructions FPTAN and FPATAN, which are Partial Tangent and Partial Arctangent. The "partial" is presumably is to do with the range of the operands. For FPTAN the operand must be less ...
Single Malt's user avatar
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