Claude-skill-registry fpu-expert

Expert on K1810VM87 (Intel 8087) floating-point coprocessor for ES-1841. Provides guidance on FPU registers, data types, instructions, exception handling, and CPU-FPU synchronization.

install

source · Clone the upstream repo

git clone https://github.com/majiayu000/claude-skill-registry

Claude Code · Install into ~/.claude/skills/

T=$(mktemp -d) && git clone --depth=1 https://github.com/majiayu000/claude-skill-registry "$T" && mkdir -p ~/.claude/skills && cp -r "$T/skills/data/fpu-expert" ~/.claude/skills/majiayu000-claude-skill-registry-fpu-expert && rm -rf "$T"

manifest: skills/data/fpu-expert/SKILL.md

source content

FPU Expert - K1810VM87 / Intel 8087

Expert knowledge for the ES-1841's optional math coprocessor.

Key Specifications

Parameter	Value
Chip	K1810VM87 (Soviet 8087 clone)
Data Types	16/32/64-bit integer, 32/64/80-bit float, 80-bit packed BCD
Registers	8 × 80-bit stack (ST0-ST7)
Status	Control, Status, Tag words
I/O Ports	`F0h` - `FFh` (escape handler)
Exception	`IRQ 13` (via `INT 75h` on AT, varies on XT)

Register Stack

┌────────────────────────────────────────┐
│  ST(7)  │ 80-bit extended precision    │
├─────────┼──────────────────────────────┤
│  ST(6)  │                              │
├─────────┤                              │
│  ST(5)  │                              │
├─────────┤     Register Stack           │
│  ST(4)  │                              │
├─────────┤                              │
│  ST(3)  │                              │
├─────────┤                              │
│  ST(2)  │                              │
├─────────┤                              │
│  ST(1)  │                              │
├─────────┼──────────────────────────────┤
│  ST(0)  │ Top of Stack (TOS)           │
└─────────┴──────────────────────────────┘

Data Formats

Type	Bits	Range
Word Integer	16	-32768 to +32767
Short Integer	32	-2×10⁹ to +2×10⁹
Long Integer	64	-9×10¹⁸ to +9×10¹⁸
Short Real	32	±1.2×10⁻³⁸ to ±3.4×10³⁸
Long Real	64	±2.2×10⁻³⁰⁸ to ±1.8×10³⁰⁸
Temp Real	80	±3.4×10⁻⁴⁹³² to ±1.2×10⁴⁹³²
Packed BCD	80	18 digits

Key Instructions

Category	Examples
Load/Store	FLD, FST, FSTP, FILD, FIST
Arithmetic	FADD, FSUB, FMUL, FDIV, FSQRT
Compare	FCOM, FCOMP, FTST
Transcendental	FSIN, FCOS, FPTAN, F2XM1, FYL2X
Control	FINIT, FWAIT, FSTCW, FLDCW

CPU-FPU Synchronization

; FWAIT/WAIT required before reading FPU results
        FLD     QWORD [value]
        FSQRT
        FWAIT                   ; Wait for FPU to complete
        FST     QWORD [result]

Exception Handling

8087 exceptions:

Invalid operation
Denormalized operand
Zero divide
Overflow
Underflow
Precision (inexact)

ES-1841 Notes

Optional coprocessor (not always installed)
Software should detect presence before use
AlphaDOS may not fully support FPU

References

See references/ for detailed documentation.