Sinclair ZX80 / ZX81 / Z88 Forums

Thank you, Mark , for time to provide this invaluable guidance. For those following along, the link he is referring to is: https://www.sinclairzxworld.com/viewtopic.php?p=16720#p16720 where Ian posted PokeMon 's circuit. Borrowing heavily from that thread (thanks guys!) and Mark's post, here's how I...

What I've understood so far: [1] By preventing the RAM pack from connecting /RAMCS' to +5V is that the A14-based determination (0=>ROM, 1=>RAM) sent from the ULA is allowed to reach the onboard 1K RAM. Because otherwise if the RAM pack +5V were allowed, this would "over-rule" the /RAMCS' signal at t...

Thanks guys, I've got me some reading to do. In the meantime, putting electrical tape over 2A (and of course checking for non-continuity prior to switching on) does successfully pass the K test. However there is not the 16K "delay" and the DIM(3000) program above gives me 4/10 i.e. it runs out of me...

I don’t remember which topic it was in, and trying to find the correct magical search term is tricky… Tricky but not impossible when given a helpful hint, thanks Mark . Using this, and inspired by the internal 1K memory being addressed at $4000, I went with the terms "A14 memory" and landed on the ...

Expat Brit now in Canada who started with a ZX81 kit, which due to its arrival time :roll: was supplied also with Games 1 - epics like Orbit, Life and such. Ah the smell of solder and getting it finally to work on a Ferguson 12" TV. From there, moved on to the Spectrum (still remember that Horizons ...

I have a Sinclair ZX16K RAM Issue 3 that "doesn't work". When plugged in and powered up on an otherwise known working ZX81, it just sits there. When I remove the RAM and power up, K. I've put a scope on pretty much everything on the pack, and the only stuck line seems to be /CAS - it is jammed high-...