Sinclair ZX80 / ZX81 / Z88 Forums

Ok so i found at least the answer, but not the solution just yet. Getting the RAM to fully work as a ROM-ghost seems a little more tricky then i thought. A0 - A8 and an alternate set of those make things a little more complex. Still the idea i had was to use the standard video routine, using differe...

Just when i thought i was done, Of course not ! Something i forgot about. Does the Rom actually write to the 0000h - 8000h as part of the screen routine ? I once saw a map of what is what in the ROM, couldn't find it straight away but i'll keep looking of course it shouldn't be to hard to fix, i jus...

Hah ! That works !! in the end i used !(A15) || !MI (instead of !(A15 || A14) || !MI )I did need to make some space on the board now, since i need to add one more IC :D But i wanted to move the backup battery anyway (or the switch to turn it on and off at least) and i'll use one of the spare OR-gate...

Ok, ehm Yes you have a point, that area is only enabled when !MI is High, so i need to do something like this.

(i've edited this post..) This is the final version for now (that is a contradiction in terms)

So now I have RAM also for the 2000h -3FFFh but i don't seem to be able to execute from there, why is that ?

I thought i'd better post this at the end of this thread as well, now the schematic looks like this. http://i57.tinypic.com/1zel3yw.jpg 0-8K ROM 8-16K Executable code (mirror 40-48K) 16 -32K RAM (mirror 48-64K) 32 -48K Data RAM 48 -64K Mirror to 16-32K It should be possible to execute code from ther...

Another day passed and in 3 steps i progressed. Now the schematic looks like this. http://i57.tinypic.com/1zel3yw.jpg 0-8K ROM 8-16K Executable code (mirror 40-48K) 16 -32K RAM (mirror 48-64K) 32 -48K Data RAM 48 -64K Mirror to 16-32K I haven't managed to execute anything from 8-16K yet, but i think...

Of course the mind hardly ever stops to think about these things, It is almost as if the process continues in the background. Then the other thing i was wondering about, downloading some .P from some site, what section of memory is being used to store the HiRes initially, 'cause if that would be in ...

Thank you all very much for your support. I am so happy it works, Now when i finish the Zaks book again, I will get into the Nitty Gritty of it all. To be Continued !

olofsen wrote:Does http://bodo4all.cwsurf.de/zx/25thanni.html work?

Yes it Does !!!