Macintosh Classic II FPU Card v2
author: Tobrew
2 layer board of 2.70 x 2.56 inches (68.6 x 65.0 mm)
Uploaded:
June 23, 2026
Shared:
June 23, 2026
Total Price:
$34.55
Expansion card that adds an MC68882 FPU to your Macintosh Classic II. The board has two layers to keep the PCB cost down. It offers a switchable clock source between the system clock (16 MHz, synchronous operation) and a crystal oscillator on the board (20,32, or 40 MHz, asynchronous operation depending on your crystal and FPU chip. If you just want a stock 16MHz FPU, leave off the oscillator and use a MC68882FN16A chip). If you want to overclock, use a faster FPU chip such as a MC68882FN40A, and the appropriate oscillator. It has been shown that the FPU can be overclocked up to 40MHz, but based on experience, keeping it around 25-33MHz maintains better CPU performance.
I added a pad for an optional 1206 LED and a spot for a 200ohm resistor.
Project by Marcin Dymczyk, Modifications by me
Expansion card that adds an MC68882 FPU to your Macintosh Classic II. The board has two layers to keep the PCB cost down. It offers a switchable clock source between the system clock (16 MHz, synchronous operation) and a crystal oscillator on the board (20,32, or 40 MHz, asynchronous operation depending on your crystal and FPU chip. If you just want a stock 16MHz FPU, leave off the oscillator and use a MC68882FN16A chip). If you want to overclock, use a faster FPU chip such as a MC68882FN40A, and the appropriate oscillator. It has been shown that the FPU can be overclocked up to 40MHz, but based on experience, keeping it around 25-33MHz maintains better CPU performance.
I added a pad for an optional 1206 LED and a spot for a 200ohm resistor.
Project by Marcin Dymczyk, Modifications by me
