GZ/80S - 20MHz Z-80 PCPI Applicard compatible Apple CP/M card

The PCPI Appli-Card was the first single board computer style CP/M card for the apple II. It featured a 6MHz Z-80 CPU paired with 64KB of RAM and 2KB of ROM. Thanks to the high clock and zero wait states DRAM accesses the card performed almost 3 times as fast as the Microsoft SoftCard. The GZ/80-B00 is a new implementation of the PCPI card with a 20MHz Z-80 CPU and 512KB of static RAM.

Schematics

The GZ/80s is a reimplementation of the PCPI Applicard with an on board 448K memory expansion.
The card is a complete Z80 SBC (Single Board Computer) with its dedicated ROM (U4) and RAM (U3). The schematics is identical to the earlier GZ80s-B00 with many components converted to SMD. The Z80 communicates to the Apple through a pair of 8-bit registers (U1 and U2) mapped in the Z80 I/O space. The Z80 I/O space is decoded by U13 into 8 separate Chip Selects. Refer to the table below for the mapping. U10/U16 generate the Z80 clock. U15B divides the Z80 clock by 2 and provides it to the expansion bus J1. U14 decodes the apple card I/O space to provide access to the card I/O registers. The U8 GAL integrates the remaining glue logic to generate the RAM and ROM chip selects and the high order bits of the RAM based on the bank register settings.

Performance

To evaluate the performance we have used a simple basic program that draws the Mandelbrot set in ASCII.