ZXMUX

ZXMUX replaces the multiplexer used in ZX Spectrum and Sinclair QL and known as:

• AMSTRAD 40058
• PCF1306P
• ZX8401

The SMD chips are connected exactly like in ZX Spectrum 48kB issue 3. The original multiplexer must be removed.

The first versions I made were designed for precise (GOLD) socket, to be mounted under it. There were big holes (1.4mm) for the socket. The socket required some cuts to make more place for the SMD chips. The board had to be not thicker than 0.7mm for best results. Another precise socket have had to be soldered to ZX Spectrum board.

In new ZXMUX board version 40 short (7mm) piece of wire (0.5mm) must be soldered (holes are 0.6mm). This is a bit of work, but more cheaper than two precise sockets. This allows standard socket to be used on ZX board and is more flexible.

In plans

I want to separate ULA multiplexer and Z80 multiplexer into two boards. Then, use latches on Z80CPU address that will remember the address while waiting for ULA to be free to write memory. This, together with similar latch on data lines and 4MB RAM upgrade should allow to use faster CPU clock with no slowing by ULA.

Files for download

zxmu-006.png 22.6kB (2004-12-06 23:32)

Schematics of ZXMUX v006.

zxmu-006.zip 21.7kB (2004-12-06 23:32)

ZXMUX v006. Eagle data files.