A new version of this project is available here
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.
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 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.
|0xh/1xh||write data register (Z80 to apple)||U2|
|2xh/3xh||read data register (apple to Z80)||U3|
|4xh/5xh||I/O register full||apple data U11A (bit 7), Z80 data U11B (bit 0)|
|8xh/9xh||Reserved for optional CTC|
|axh/bxh||Reserved for optional Apple IRQ|
|cxh/dxh||RAM Bank register||U9 (bit 1,2,3 bank address, bit 6 common area enable)|
To evaluate the performance we have used a simple basic program that draws the Mandelbrot set in ASCII.
|Card||Clock||FRACT.BAS execution time (mm:ss)|