The SP ROM by Comprocsys Ltd was an add-on card for the ZX81 that provided 256 x 192 bitmapped graphics, reading and writing of EPROMs and communication with peripherals through a Zilog 8255 PIA chip. It could be used in conjunction with the Comprocsys ASZMIC ROM or without (via ZX81 BASIC commands). Comprocsys External Card Advert […]