The Glitch Works GW-SDK80-RAM1 is a small mezzanine board which allows Intel MCS-80 System Design Kits (SDK-80s) to be expanded to 64K of RAM. It also provides ROM remapping and disable capability, with two external jumper wires. The GW-SDK80-RAM1 is a drop-in board, it replaces several ICs on the SDK-80. If your SDK-80 is socketed, this requires no actual modification to the SDK-80 itself, and can be reversed by unplugging the GW-SDK80-RAM1 and reinstalling the original chips it replaces.

The GW-SDK80-RAM1 is compatible with JEDEC 62256-type static RAMs, as well as FM18W08 ferroelectric RAM (FeRAM). 28C256 EEPROMs are also compatible, though they are of limited use in this board. Kits and assembled boards are provided with machine pin headers for mounting in machine pin sockets; if your SDK-80 uses dual-wipe sockets, we highly recommend upgrading to quality machine pin sockets.

In its default configuration with no control wires jumpered in, the GW-SDK80-RAM1 appears as 60K of static RAM from 0x1000 - 0xFFFF. Normal SDK-80 ROM is decoded through the mezzanine board, so existing ROMs in the SDK-80 ROM sockets will appear at their normal addresses (0x0000 - 0x0FFF). When TP1 is grounded, ROM is relocated to 0xF000 - 0xFFFF. When TP2 is grounded, ROM is disabled entirely and the entire SDK-80 memory space is filled with static RAM on the GW-SDK80-RAM1. TP1 and TP2 may be connected to any available 8255 PPI output pins for software control.

ICs replaced by the GW-SDK80-RAM1 include:

• A11 and A12, Intel 8212 address buffers
• A13 8205/3205 ROM address decoder
• A18 8205/3205 RAM address decoder
• All 2111/8111 static RAMs

You can read about the development of the GW-SDK80-RAM1 on our website:

http://www.glitchwrks.com/2019/04/01/gw-sdk80-ram1

The Intel SDK-80 pictured in this listing is NOT included and is used to demonstrate installation only. The first image shows the bare board option, while the last two show the fully assembled and tested option.