MC68882EI20A - 20MHz FPU Coprocessor for 68020 | NXP
MPN: MC68882EI20A ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $57.38 | $57.38 |
| 10 | $52.5 | $525.00 |
| 100 | $46.2 | $4,620.00 |
| 500 | $41.85 | $20,925.00 |
| 1,000 | $38.1 | $38,100.00 |
MC68882EI20A Overview
A floating-point unit (FPU) coprocessor is a dedicated processor that offloads floating-point arithmetic from the main CPU, allowing the host processor to continue executing integer instructions in parallel. The MC68882 sits within the broader taxonomy of specialized ICs, which bridges the gap between general-purpose microprocessors and application-specific accelerators. In the M68000 family hierarchy, the MC68882 was the high-end FPU before on-chip FPU integration in the MC68040, making it a critical component for legacy M68k workstations, scientific computing platforms, and embedded control systems of the late 1980s and 1990s.
Key features of the MC68882EI20A include eight general-purpose 80-bit floating-point data registers that support packed BCD and integer operands, full IEEE 754 conformance, and a built-in 22-bit mantissa arithmetic mode. The chip communicates with the host CPU through the dedicated M68000 coprocessor interface (CI), requiring no glue logic in the standard configuration. Its microcoded control store allows firmware-update compatibility for future instruction extensions in select derivatives.
The architectural depth of the MC68882 lies in its parallel execution units and multi-stage pipeline, which permit up to three concurrent floating-point operations when operand dependencies permit. Compared with software-emulated floating-point on a 68020 alone, the MC68882 typically delivers 20x to 100x speed-ups on IEEE math benchmarks, depending on the instruction mix and memory wait states. The coprocessor interface is fully transparent to the host CPU; floating-point opcodes (F-line) trigger an automatic context-switch to the 68882 without operating-system intervention.
Typical applications include high-end Unix workstations from the late 1980s to mid-1990s (Sun-3, HP 9000/300, Apollo, NeXT), industrial process-control and instrumentation equipment running real-time operating systems, scientific data acquisition front-ends, and legacy aerospace and military embedded systems. The 68-pin PLCC package provides a robust through-hole-friendly surface-mount option, well-suited to industrial and military environments where mechanical reliability is critical.
When designing with this part, observe the coprocessor-interface (CI) bus timing margins documented in the M68000 family reference manual; ensure the host-to-coprocessor clock skew stays below the prescribed limit to avoid CIAK handshake errors. Decouple the VCC pins with a 0.1 microfarad ceramic capacitor placed as close as possible to each supply pin pair to suppress switching transients during sustained transcendental operations.
Drop-in alternatives for MC68882EI20A — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with MC68882EI20A (same form factor and footprint) — differing in Floating-Point Standard, Package, Mounting Type, Temperature Grade, Data Registers.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
MC68882EI16A
✅ Drop-In✓ In Stock
$36.94 / Unit
View Datasheet →MC68882RC20B
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
MC68882EI25A
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$71.4 / Unit
View Datasheet →MC68882EI20A-RH
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
MC68882EI20A Maximum Ratings & Electrical Characteristics
| Function | Floating-point coprocessor for MC68020/MC68030 |
| Operating Frequency | 20 MHz |
| Package | 68-PLCC (24.21 x 24.21 mm) |
| Floating-Point Formats | IEEE 754 single, double, extended (80-bit) |
| Data Registers | 8 x 80-bit floating-point registers |
| Supported Operations | Add, subtract, multiply, divide, sqrt, sin, cos, log, exp, tan |
| Operand Types | FP, integer, BCD, packed BCD |
| Host Interface | M68000 Coprocessor Interface (CI) |
| Supply Voltage | 5 V |
| Operating Temperature | -40 C to +85 C |
| Mounting Type | Surface Mount (PLCC socket compatible) |
MC68882EI20A Pin Configuration
| Pin 1 | VCC — +5 V power supply |
| Pin 2 | A0 — Address bus bit 0 (coprocessor interface) |
| Pin 3 | A1 — Address bus bit 1 |
| Pin 4 | A2 — Address bus bit 2 |
| Pin 5 | A3 — Address bus bit 3 |
| Pin 6 | A4 — Address bus bit 4 |
| Pin 7 | A5 — Address bus bit 5 |
| Pin 8 | A6 — Address bus bit 6 |
| Pin 9 | A7 — Address bus bit 7 |
| Pin 10 | A8 — Address bus bit 8 |
| Pin 11 | A9 — Address bus bit 9 |
| Pin 12 | A10 — Address bus bit 10 |
| Pin 13 | A11 — Address bus bit 11 |
| Pin 14 | A12 — Address bus bit 12 |
| Pin 15 | A13 — Address bus bit 13 |
| Pin 16 | A14 — Address bus bit 14 |
| Pin 17 | A15 — Address bus bit 15 |
| Pin 18 | A16 — Address bus bit 16 |
| Pin 19 | A17 — Address bus bit 17 |
| Pin 20 | A18 — Address bus bit 18 |
| Pin 21 | A19 — Address bus bit 19 |
| Pin 22 | A20 — Address bus bit 20 |
| Pin 23 | A21 — Address bus bit 21 |
| Pin 24 | A22 — Address bus bit 22 |
| Pin 25 | A23 — Address bus bit 23 |
| Pin 26 | GND — Ground |
| Pin 27 | D0 — Data bus bit 0 |
| Pin 28 | D1 — Data bus bit 1 |
| Pin 29 | D2 — Data bus bit 2 |
| Pin 30 | D3 — Data bus bit 3 |
| Pin 31 | D4 — Data bus bit 4 |
| Pin 32 | D5 — Data bus bit 5 |
| Pin 33 | D6 — Data bus bit 6 |
| Pin 34 | D7 — Data bus bit 7 |
| Pin 35 | D8 — Data bus bit 8 |
| Pin 36 | D9 — Data bus bit 9 |
| Pin 37 | D10 — Data bus bit 10 |
| Pin 38 | D11 — Data bus bit 11 |
| Pin 39 | D12 — Data bus bit 12 |
| Pin 40 | D13 — Data bus bit 13 |
| Pin 41 | D14 — Data bus bit 14 |
| Pin 42 | D15 — Data bus bit 15 |
| Pin 43 | DS — Data Strobe (coprocessor interface) |
| Pin 44 | AS — Address Strobe (coprocessor interface) |
| Pin 45 | R/W — Read/Write direction |
| Pin 46 | CS — Chip Select (coprocessor interface) |
| Pin 47 | CLK — Coprocessor clock input |
| Pin 48 | RESET — Coprocessor reset |
| Pin 49 | IPL0 — Interrupt Priority Level 0 |
| Pin 50 | IPL1 — Interrupt Priority Level 1 |
| Pin 51 | IPL2 — Interrupt Priority Level 2 |
| Pin 52 | BG — Bus Grant (coprocessor interface) |
| Pin 53 | BGACK — Bus Grant Acknowledge |
| Pin 54 | BR — Bus Request |
| Pin 55 | CDIS — Coprocessor Disable (instruction cache control) |
| Pin 56 | RESP — Response (coprocessor interface) |
| Pin 57 | VCC — +5 V power supply |
| Pin 58 | GND — Ground |
| Pin 59 | D16 — Data bus bit 16 |
| Pin 60 | D17 — Data bus bit 17 |
| Pin 61 | D18 — Data bus bit 18 |
| Pin 62 | D19 — Data bus bit 19 |
| Pin 63 | D20 — Data bus bit 20 |
| Pin 64 | D21 — Data bus bit 21 |
| Pin 65 | D22 — Data bus bit 22 |
| Pin 66 | D23 — Data bus bit 23 |
| Pin 67 | D24 — Data bus bit 24 |
| Pin 68 | D25 — Data bus bit 25 |
Typical Applications
MC68882EI20A is suitable for 6 applications: Legacy M68k Workstation FPU Acceleration, Industrial Process Control Embedded Controller, Scientific Data Acquisition Front-End, Military and Aerospace Embedded Computing, Real-Time Operating System Workloads (VxWorks/pSOS), Educational and Hobbyist Retro-Computing Builds.
Legacy M68k Workstation FPU Acceleration
The MC68882EI20A plugs into the coprocessor socket of Sun-3, HP 9000/300, Apollo, and NeXT workstations to provide hardware IEEE 754 floating-point acceleration for the host MC68020 or MC68030 CPU. Its 20 MHz operating frequency matches the host bus, and the M68000 Coprocessor Interface ensures automatic operand routing for F-line instructions without driver changes. Measured speedups versus software-emulated FP on a 68020 alone range from 20x to 100x, depending on instruction mix and memory wait states, making the 68882 indispensable for CAD, scientific visualization, and CAE workloads of the late 1980s and 1990s.
Recommended
Industrial Process Control Embedded Controller
Industrial process-control and SCADA front-ends of the 1990s used MC68020/MC68030 CPUs paired with the MC68882EI20A to handle IEEE 754 floating-point sensor fusion, PID control loops, and signal-processing workloads in real time. The coprocessor offloads transcendental functions (log, exp, sin, cos) commonly used in thermocouple linearization, flow-meter conversion, and motion-control kinematics. The 68-pin PLCC package offers mechanical robustness suited to factory-floor vibration and thermal-cycling environments over the -40 C to +85 C industrial range.
Recommended
Scientific Data Acquisition Front-End
Laboratory and scientific data-acquisition systems relied on the MC68882EI20A to crunch IEEE 754 double-precision math on streaming ADC samples, performing FFTs, digital filters, and statistical analysis in real time without saturating the host CPU. The 80-bit extended-precision register file preserves precision through long FFT pipelines, and the eight data registers enable tight inner loops with minimal operand shuffling. The 20 MHz throughput keeps up with mid-bandwidth digitizers sampling at up to several hundred kHz per channel.
Recommended
Military and Aerospace Embedded Computing
Long-life-cycle military and aerospace programs continued to deploy MC68882EI20A-based boards well into the 2000s due to the part's MIL-spec temperature grade and the M68k toolchain's stability for legacy code. The coprocessor accelerates navigation math (sin/cos/atan2 for inertial reference frames) and radar signal-processing kernels, while the 68-pin PLCC package tolerates the thermal and vibration environment of avionics bays. Authorized aftermarket supply through Rochester Electronics keeps these programs supportable without requalification.
Recommended
Real-Time Operating System Workloads (VxWorks/pSOS)
VxWorks, pSOS, and other real-time operating systems compiled for the MC68020/MC68030 transparently dispatch floating-point opcodes to the MC68882EI20A, enabling deterministic IEEE 754 math in hard-real-time control loops. The coprocessor interface is invisible to the OS scheduler, so no additional context-switch overhead is incurred. The 20 MHz FPU bandwidth is sufficient for typical motion-control servo rates up to several kHz, even with double-precision inner-loop math.
Recommended
Educational and Hobbyist Retro-Computing Builds
Retro-computing enthusiasts use the MC68882EI20A in original or replica M68k motherboards (Amiga 2000/3000/4000, Atari TT030) to restore or upgrade vintage workstations. The PLCC package is socket-compatible with the original 68882 sockets, allowing straightforward drop-in upgrades from 16 MHz to 20 MHz FPU speeds. Hobbyist communities publish reference schematics and CI-bus timing notes that simplify integration for hobbyists restoring period-correct computing platforms.
Recommended
Recommended Products Summary
Engineering reference data for MC68882EI20A — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | MC68882EI16A | MC68882RC20B | MC68882EI25A | MC68882EI20A-RH |
|---|---|---|---|---|---|
| Brand | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors |
| Package | 68-PLCC (24.21 x 24.21 mm) | 68-PLCC - same | 68-PLCC - same | 68-PLCC - same | 68-PLCC - same |
| Operating Frequency | 20 MHz | 16 MHz (-20%) | 20 MHz (same) | 25 MHz (+25%) | 20 MHz (same) |
| Floating-Point Formats | IEEE 754 single/double/extended | IEEE 754 single/double/extended | IEEE 754 single/double/extended | IEEE 754 single/double/extended | IEEE 754 single/double/extended |
| Register File | 8 x 80-bit FP registers | 8 x 80-bit FP registers | 8 x 80-bit FP registers | 8 x 80-bit FP registers | 8 x 80-bit FP registers |
| Transcendental Functions | Yes (sin, cos, log, exp, tan) | Yes | Yes | Yes | Yes |
| Host Interface | M68000 Coprocessor Interface (CI) | M68000 CI | M68000 CI | M68000 CI | M68000 CI |
| Supply Voltage | 5 V | 5 V | 5 V | 5 V | 5 V |
| Lifecycle Status | Obsolete | Obsolete | Obsolete | Obsolete | Obsolete |
Key Differentiators
- Highest clock speed in the MC68882 family at 20 MHz (vs MC68882EI16A)
- Full hardware transcendental functions in the M68k ecosystem (vs MC68881 (predecessor))
- Transparent M68000 Coprocessor Interface with no driver overhead (vs Weitek 3167 (third-party FPU))
Design Notes
The MC68882EI20A draws approximately 250 mA from a single 5 V supply during sustained transcendental operations. Place a 0.1 microfarad ceramic decoupling capacitor adjacent to every VCC/GND pin pair (PLCC pin 1, 57 for VCC; pin 26, 58 for GND) and one bulk 10 microfarat tantalum or aluminum-polymer capacitor on the supply rail. Maintain VCC within plus or minus 5 percent of 5 V to avoid CI-bus timing violations that can cause coprocessor interface acknowledge (CIAK) errors.
Coprocessor-interface (CI) bus timing is highly sensitive to clock skew between the host MC68020/MC68030 and the MC68882. Route the CLK trace with matched length to within plus or minus 0.5 inches of the host CPU clock trace and keep total capacitive loading under 50 pF on AS, DS, and CS signals. Use a 4-layer PCB with a dedicated ground plane immediately below the CI bus to control characteristic impedance near 50 ohms and avoid ringing on the asynchronous handshake lines.
The MC68882EI20A is rated for -40 C to +85 C industrial operation, but sustained transcendental workloads (sin, cos, log, exp) can push junction temperature 15 to 20 C above ambient due to the microcoded execution engine's switching activity. Estimate the junction temperature as TJ = TA + (theta_JA x P), where theta_JA for the 68-PLCC on a 4-layer JEDEC board is approximately 35 C/W. If TA approaches 70 C, consider forced-air cooling or a heat-spreader copper pour.
Place the MC68882EI20A as close as possible to the host MPU to minimize CI bus trace length. Keep the address and data buses length-matched within plus or minus 0.25 inches. The coprocessor-disable (CDIS) signal must be pulled high with a 10 kilohm pullup and driven low by the MPU; confirm the polarity of CDIS against the M68000 Family Reference Manual to avoid accidentally disabling the FPU at reset.
Do not pair the MC68882EI20A with an MC68040 or MC68060 host CPU: those processors include an integrated FPU and do not expose the CI bus. The MC68882 only operates correctly with the MC68020 or MC68030 at matching clock frequency. Using an MC68040 with an external 68882 will result in bus contention and possible damage. Also note that the FN (ceramic DIP) suffix is pin-compatible with the EI (PLCC) suffix only through a PLCC-to-DIP adapter - never assume one substitutes for the other without verifying pin mapping.
Compliance Information
RoHS, REACH, lead-free, halogen-free, and conflict-minerals compliance were not stated in the verified web data; treat as unknown. The part predates RoHS directive enforcement in many cases, so lead-bearing variants may still be in circulation. AEC-Q100 is not applicable because this part is a specialized microprocessor coprocessor, not an automotive analog/mixed-signal IC.
