Make your own free website on

ROM select circuit for ZX Spectrum

My intention with this circuit was to make possible switching diverse ROM's in two ways:

1: With button press - when you are in some program e.g. game.

2: With OUT command from software/command line. With OUT 169,n (n is 0 to 3) the desired ROM will be selected.

Lines EA14 & EA15 lead to EPROM's address lines A14 & A15. The EPROM type is 27512 - where it is possible to put 4 versions of Spectrum ROM.
After power on, always ROM section #3 will be selected, so put there your default version.

Back to start page