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edit approved Feb 13, 2019 at 14:30
psmears
edit approved Feb 13, 2019 at 14:30
psmears
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The 8087 has many instructions. Too - too many, it seems, to be encoded as part of the 8086 instructionsinstruction set. How did the Intel 8086 interface with an Intel 8087 FPU that a user added?

Consider the following x86 assembly code sample:

// c = a + b;
fld    DWORD PTR [rbp-0xc]  // a;
fadd   DWORD PTR [rbp-0x8]  // b;
fstp   DWORD PTR [rbp-0x4]  // c;

The instructions fld, fadd, and ftsp I assume are not hardwired into the 8086 circuit. So are they psuedo instructionspseudo-instructions that the assembler subsequently converts to command/data instructions for the 8086 to pass onto the 8087 appropriately?

For example fld might be encoded as command 0 and for data the value of rbp-0xc is encoded which the 8087 would know is an address in memory holding the value it needs? And then a sequence of OUT instructions are used by the 8086 to send the command and data to the 8087?

The 8087 has many instructions. Too many it seems to be encoded as part of the 8086 instructions. How did the Intel 8086 interface with an Intel 8087 FPU that a user added?

Consider the following x86 assembly code sample:

// c = a + b;
fld    DWORD PTR [rbp-0xc]  // a;
fadd   DWORD PTR [rbp-0x8]  // b;
fstp   DWORD PTR [rbp-0x4]  // c;

The instructions fld, fadd, and ftsp I assume are not hardwired into the 8086 circuit. So are they psuedo instructions that the assembler subsequently converts to command/data instructions for the 8086 to pass onto the 8087 appropriately?

For example fld might be encoded as command 0 and for data the value of rbp-0xc is encoded which the 8087 would know is an address in memory holding the value it needs? And then a sequence of OUT instructions are used by the 8086 to send the command and data to the 8087?

The 8087 has many instructions - too many, it seems, to be encoded as part of the 8086 instruction set. How did the Intel 8086 interface with an Intel 8087 FPU that a user added?

Consider the following x86 assembly code sample:

// c = a + b;
fld    DWORD PTR [rbp-0xc]  // a;
fadd   DWORD PTR [rbp-0x8]  // b;
fstp   DWORD PTR [rbp-0x4]  // c;

The instructions fld, fadd, and ftsp I assume are not hardwired into the 8086 circuit. So are they pseudo-instructions that the assembler subsequently converts to command/data instructions for the 8086 to pass onto the 8087 appropriately?

For example fld might be encoded as command 0 and for data the value of rbp-0xc is encoded which the 8087 would know is an address in memory holding the value it needs? And then a sequence of OUT instructions are used by the 8086 to send the command and data to the 8087?

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Jet Blue
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How did the 8086 interface with the 8087 FPU coprocessor?

The 8087 has many instructions. Too many it seems to be encoded as part of the 8086 instructions. How did the Intel 8086 interface with an Intel 8087 FPU that a user added?

Consider the following x86 assembly code sample:

// c = a + b;
fld    DWORD PTR [rbp-0xc]  // a;
fadd   DWORD PTR [rbp-0x8]  // b;
fstp   DWORD PTR [rbp-0x4]  // c;

The instructions fld, fadd, and ftsp I assume are not hardwired into the 8086 circuit. So are they psuedo instructions that the assembler subsequently converts to command/data instructions for the 8086 to pass onto the 8087 appropriately?

For example fld might be encoded as command 0 and for data the value of rbp-0xc is encoded which the 8087 would know is an address in memory holding the value it needs? And then a sequence of OUT instructions are used by the 8086 to send the command and data to the 8087?