SINCLAIR ZX-81 -- HIGH RESOLUTION 192x256 (CRL) Untested

About this deal

The Sinclair ZX-81 is the machine that marked the point when home computing in Britain became an activity for the general public rather than businessmen and electronics hobbyists. It is powered by a 3.5 MHz Z80A 8-bit processor and an 8 KB ROM providing a Sinclair BASIC interpreter. The ZX81 does not have native high-resolution graphics, so a graphics-capable RAM pack or software toolkit is required to enable that mode. CRL released a hi-res graphics toolkit for the ZX81 containing an interrupt routine that replaced the machine's usual display update routine, pointing the I register to a strategic ROM location and attempting to best-fit the high-resolution display to what it found there. It also exploited a ZX81 hardware feature allowing single-pixel-height characters to improve results, though at best only 128 different pixel combinations out of 256 possible ones could be achieved, making this a pseudo-HRG technique. This item is sold as untested, so buyers should verify functionality before use. It will appeal to retro computing collectors and ZX81 enthusiasts.